Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-09-03
2004-03-30
Nguyen, Thinh (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S037000
Reexamination Certificate
active
06712440
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink-jet printing apparatus and a print timing setting method for the apparatus, and more particularly, to print timing setting for an ink-jet printing apparatus which performs printing by scanning a carriage incorporating a printhead discharging ink relative to a print medium and which comprises an encoder outputting a detection signal in accordance with a predetermined distance of a carriage movement in a carriage scanning direction.
BACKGROUND OF THE INVENTION
As a data output apparatus employed in, for instance, word processors, personal computers, facsimiles or the like, printers printing desired information, such as characters and images, on a sheet-type print medium, e.g., paper, film or the like, are widely used.
For a printing method of such printers, various printing methods are known. Particularly, an ink-jet printing method recently receives attention because of its capability to perform printing without contacting a print medium such as paper, ease of color printing, and quiet printing operation. In general, such printers widely adopt a serial printing method because of its low cost and ease of downsizing. According to the serial printing method, printing is realized by reciprocally scanning a carriage, incorporating a printhead discharging ink in accordance with desired print data, in the direction orthogonal to the conveyance direction of a print medium such as paper.
Furthermore, recently a printing method called a reciprocal printing or bi-directional printing is adopted to improve printing speed. According to this method, printing is realized by discharging ink from a printhead in both forward and backward directions of a carriage movement relative to a print medium.
FIG. 3
is a view showing a relation between printhead moving speed (scanning speed) and an ink droplet landing position. Described hereinafter is a case where a printhead
301
, incorporated in a carriage (not shown), moves in the direction A in
FIG. 3
at reference speed V. The distance between the printhead
301
and print medium
305
is d. When the printhead
301
discharges an ink droplet
303
at the position
307
onto the print medium
305
at discharge speed Vd, the ink droplet
303
travels at speed and the direction represented by composite vectors of the reference speed V and discharge speed Vd. The landing position of the ink droplet
303
on the print medium
305
is a position
306
, which is deviated in the direction A by a distance &dgr; from the position
307
where the printhead
301
has actually discharged the ink droplet
303
.
Assuming that the forward scan of the printhead
301
is the direction A, the backward scan of the printhead
301
is the direction B in a case of performing reciprocal printing. If the printhead
301
discharges ink in the backward scan at the same position as the position
307
where the ink droplet
303
is discharged in the forward scan, the ink droplet
303
lands on a position
310
which is deviated by a distance &dgr; in the direction opposite to the landing position
306
with respect to the position
307
. As a result, even if an ink droplet is discharged at the same position in the forward and backward scans, the landing position on the print medium deviates by the distance from
306
to
310
, i.e., 2×&dgr;.
In order to eliminate the landing position deviation between the forward and backward scans, the ink-jet printing apparatus performs registration adjustment in reciprocal printing, making use of the fact that an ink droplet is normally discharged in a region where a printhead moves at constant speed. More specifically, the printer is controlled such that it discharges an ink droplet at timing
313
in the backward scan, that is the timing at which a predetermined delay time (delay)
312
is added to the one previous timing
311
, instead of the timing
307
that corresponds to the discharge position
307
in the forward scan.
However, recently there are further demands for an improved speed and low cost of printers. In order to meet the demands, attempts have been made to perform printing not only in a region where a printhead moves at constant speed but also in a region where a printhead accelerates or decelerates, or to employ a low-cost motor and components thereof.
In the accelerating and decelerating regions, the printhead moving speed changes. Furthermore, employing a low-cost motor and control components causes cockling of the motor in the constant-speed motion region and causes speed variations due to negatively influenced servo precision. As a result, an ink droplet is discharged in a state where the printhead moving speed varies, and the landing position of the ink droplet deviates from a target position.
When the printhead moving speed varies, landing positions in the forward and backward scans can no longer be adjusted by the registration adjustment using a predetermined delay. Therefore, it is necessary to deviate the landing position of the ink droplet by a predetermined distance. In the region where the printhead moving speed varies, mere delaying of the discharge timing by a predetermined time, as has conventionally been done, still generates an ink landing position deviation for a distance corresponding to the speed variations.
SUMMARY OF THE INVENTION
The present invention has been proposed to solve the conventional problems, and has as its object to provide an ink-jet printing apparatus capable of performing registration adjustment in reciprocal printing even if printhead moving speed varies.
Another object of the present invention is to provide a print timing setting method for an ink-jet printing apparatus capable of performing registration adjustment in reciprocal printing even if printhead moving speed varies.
According to the present invention, the foregoing object is attained by providing an ink-jet printing apparatus performing printing by reciprocally scanning a carriage, incorporating a printhead, relative to a print medium, comprising: detection means for outputting a detection signal in accordance with a predetermined distance of a movement of the carriage in a carriage scanning direction; timing signal output means for generating a timing signal in correspondence with a period of the detection signal; time interval detection means for timing a time interval of the detection signal; memory means for storing as reciprocal registration adjustment information a ratio between the time interval of the detection signal and a delay time of the timing signal; delay time setting means for obtaining a delay time of the timing signal based on the information read out from the memory means and the time interval of the detection signal when performing printing in a backward scan; delay signal output means for outputting a delay signal, obtained by delaying the timing signal, in accordance with the delay time; and driving means for driving the printhead based on the delay signal.
Furthermore, the foregoing object is attained by providing a print timing setting method for an ink-jet printing apparatus, which performs printing by reciprocally scanning a carriage, incorporating a printhead, relative to a print medium and includes detection means for outputting a detection signal in accordance with a predetermined distance of a carriage movement in a carriage scanning direction, comprising the steps of: generating a timing signal in correspondence with a period of the detection signal; timing a time interval of the detection signal; storing as reciprocal registration adjustment information a ratio between the time interval of the detection signal and a delay time of the timing signal in memory means; obtaining a delay time of the timing signal based on the information read out from the memory means and the time interval of the detection signal when performing printing in a backward scan; outputting a delay signal, obtained by delaying the timing signal, in accordance with the delay time; and driving the printhead based on the delay signal.
In other words, ac
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Thinh
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