Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2003-01-29
2004-09-28
Nguyen, Lamson (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06796626
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image printing apparatus using a printhead and, more particularly, to an image printing apparatus capable of supplying a stable power to the printhead and printing a high-quality image.
BACKGROUND OF THE INVENTION
Printers which print desired information such as characters or images on a sheet-like printing medium such as a paper sheet or film are adopted as an information output apparatus for a word processor, personal computer, facsimile machine, or the like.
The printing method of the printer includes various methods. An ink-jet method has recently received a great deal of attention because it can perform non-contact printing on a printing medium such as a paper sheet, can easily print a full-color image, and is quiet. As an ink-jet arrangement, a serial printing method is generally widely used in terms of low cost and easy downsizing. In the serial printing method, a printhead for discharging ink in accordance with desired printing information is mounted. Information is printed by reciprocally scanning the printhead in a direction perpendicular to the feed direction of a printing medium such as a paper sheet.
FIG. 6
is a block diagram showing a supply system which supplies power and an image signal from a conventional ink-jet printer main body to the printhead.
FIG. 7
is a side view showing a carriage electric mounting portion mounted on the carriage of the conventional printer.
In the conventional ink-jet printer, a power supply for supplying power is incorporated as a power supply unit board
103
in the printer main body, as shown in
FIG. 6
, or is connected as an AC adapter (not shown) to the printer main body. Necessary power is supplied to a printhead
102
connected to a carriage board A
100
mounted on the carriage via a power supply wiring pattern
105
on a main body board
104
and via a flexible wiring conductor (flexible wiring board or wiring line called “flat cable”)
101
.
Recent printers are required to achieve high quality equivalent to a photograph (to be referred to as photographic quality hereinafter) and performance of printing an image at a high speed (to be referred to as high-speed printing hereinafter). The ink-jet printer technique has remarkably been developed, and the above-described conventional power supply method poses the following problems.
More specifically, to meet both the photographic quality and high-speed printing, it is necessary that “small ink droplets are discharged from the printing elements of the printhead
102
to a printing medium (e.g., printing sheet) as much as possible per unit time”. The ink-jet printer must satisfy this demand. For this purpose, the electric energy (power) per unit time necessary for printing to be supplied to the printhead
102
must be increased.
The power supply for supplying power is generally a constant-voltage power supply. To meet both the photographic quality and high-speed printing, a current (I
Prhd
) supplied to the printhead
102
as a load is increased by the load.
The above-mentioned flexible wiring conductor
101
generates the following voltage drop (V
Drop
) owing to its wiring resistance (R
Frex
):
V
Drop
=I
Prhd
×R
Frex
The voltage drop V
Drop
) changes depending on an image to be printed by the printhead
102
. With an excessively large voltage drop V
Drop
), a voltage supplied from the power supply for supplying power becomes lower than a voltage necessary for the printhead
102
to print an image. As a result, ink necessary to print an image may not be able to be supplied from the printing element.
To solve this problem, the voltage drop (V
Drop
) by the wiring resistance (R
Frex
) is suppressed to be small. In order to reduce the wiring resistance (R
Frex
) of the flexible wiring conductor
101
, the power supply line has been made thick or the number of power supply lines has been increased.
In these measures, the flexible wiring conductor
101
functions as a physical load to the carriage, and causes various problems: (1) the load of the carriage driving motor increases; (2) the rigidity of the power supply line increases to impair the flexibility of the wiring conductor
101
; and (3) the cost of the wiring conductor
101
increases.
Especially in a large A0-size ink-jet printer, the flexible wiring conductor
101
is longer than that of an A4-size home printer, and exceeds 1 m including internal wiring. Thus, the above-described problems become serious, and electric energy (power) necessary for printing to be supplied to the printhead
102
cannot be satisfactorily supplied.
As one solution for the problem, an example of mounting a power supply for supplying power on the carriage is disclosed in Japanese Patent Laid-Open No. 10-6505 (Hewlett-Packard) “Carriage-Mounted Printed Circuit Assembly to Which Pen Driver and Power Supply Circuit Are Assembled”.
When, however, the arrangement disclosed in Japanese Patent Laid-Open No. 10-6505 was applied to an actual ink-jet printer, the following problems 1 and 2 occurred, and it was found that the ink-jet printer could not be easily constituted.
[Problem 1]
No mounting space can be ensured on a carriage board A
110
due to restrictions on the printing direction.
FIG. 8
is a block diagram showing the power supply system of an ink-jet printer when a power supply (DC/DC converter) for supplying power is mounted on the carriage board A
110
.
FIG. 9
is a side view showing a carriage electric mounting portion when the power supply for supplying power is mounted on the carriage board A
110
.
In printing an image, as shown in
FIG. 7
, a conventional ink-jet printer discharges ink droplets from the lower surface of the printhead
102
, and a printing sheet as a printing medium is fed below the lower surface.
To mount the power supply for supplying power on the carriage board A
110
, as shown in
FIG. 9
, the carriage board in
FIG. 7
must be enlarged upward, and the power supply must be mounted on the enlarged carriage board. However, if the board is enlarged upward, as shown in
FIG. 9
, the board hits against the cover of the ink-jet printer main body. The conventional outer cover cannot be directly used, and the specifications must be changed to enlarge the outer cover.
This specification change increases not only the manufacturing cost but also the ink-jet printer installation volume. This degrades the compactness in installation which is one of important product properties of the ink-jet printer. Also when the carriage board A
110
is enlarged (not shown) in the carriage moving direction (main scanning direction, i.e., right-to-left direction viewed from the front of the printer) in order to mount the power supply for supplying power, the outer case must be enlarged in the right-to-left direction, increasing the installation area. Also in this case, the same problems as those described above occur.
[Problem 2]
Large-format printers are mainly for business purposes. Due to heavy duty, a load change absorbing decoupling capacitor (also serving as an output capacitor for a DC/DC converter) must be exchanged, which is difficult to perform.
In
FIG. 6
, the current I
Prhd
) supplied from the power supply unit board
103
to the printhead
102
changes in accordance with the printing image, as described above. The printing elements (nozzles) of the printhead
102
change from “a state in which no ink is discharged” to “a state in which all nozzles assigned for simultaneous driving discharge ink”. The load change changes the driving voltage of another head board (HB) mounted in the printhead. To prevent the voltage change, a load change absorbing decoupling capacitor
106
is mounted.
To satisfy both the photographic quality and high-speed printing, the electric energy amount (power) supplied to the printhead increases in proportion to the load. Along with this, the load changes greatly, and a large ripple current (I
cripple
) flows into the load change absorbing decoupling capacitor
106
. The decoupling capacitor
106
generates heat by
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Mouttet Blaise
Nguyen Lamson
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