Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2000-01-28
2002-05-14
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S010000, C347S011000
Reexamination Certificate
active
06386664
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ink-jet recording apparatus having an ink-jet recording head capable of jetting ink from nozzles to a recording medium according to recording data. In particular, this invention relates to an ink-jet apparatus which can prevent viscosity of ink in nozzles from increasing.
BACKGROUND OF THE INVENTION
An ink-jet recording apparatus such as an ink-jet printer or an ink-jet plotter has a recording head that is movable in a main scanning direction. The recording head has nozzles capable of jetting ink. For example, the nozzles are communicated to pressure chambers which can expand and contract respectively. In the case, the ink in the nozzles can be jetted by expanding and contracting of the pressure chambers. The ink-jet recording apparatus is also adapted to feed a recording medium such as a recording paper in a subordinate scanning direction, which is perpendicular to the main scanning direction. Thus, the nozzles of the recording head can jet ink in order to from an image (or a character) on the recording medium in cooperation with moving the recording head and the recording medium according to recording data.
The ink in the nozzles of the recording head is exposed to air. Thus, solvent of the ink such as water may gradually evaporate to increase a viscosity of the ink in the nozzles. In the case, quality of the printed (recorded) image may deteriorate because the ink having a great viscosity maybe jetted in a direction deviated from a normal direction.
To prevent the viscosity of the ink in the nozzles from increasing, some measures have been proposed. One of the measures is to cause a meniscus of the ink to minutely vibrate in order to stir the ink. The meniscus means a free surface of the ink exposed at an opening of a nozzle.
For the purpose of stirring the ink, the meniscus may be caused to vibrate i.e. move toward a jetting direction of the ink and toward a contracting direction opposed to the jetting direction by turns in such a manner that the ink may not be jetted. The vibration of the meniscus can be also carried out by expanding and contracting of a corresponding pressure chamber. Owing to the vibration of the meniscus, the ink at the opening of the nozzle may be stirred to prevent the viscosity of the ink from increasing.
The stirring of the ink may be carried out during a scanning operation including one or more recording operation. For example, the stirring may be carried out while a carriage carrying the recording head is being accelerated just after starting of a main scanning, or while a recording operation for a nozzle is being carried out. In the stirring while the carriage is being accelerated, a micro-vibrating operating signal for micro vibrating is supplied to the recording head to cause all menisci in the nozzles to minutely vibrate. In the stirring while the recording operation is being carried out, a pulse signal for micro vibrating is generated from a jetting operating signal for jetting ink, and the pulse signal is supplied to the recording head so that the ink in the other nozzles not in the other recording (jetting) operation may be stirred.
Recently, such a type of ink-jet recording apparatus is requested to more improve the quality of the printed image and to enlarge an area of the recording medium capable of being recorded in a width direction thereof.
Thus, a volume of ink jetted at a time has been made smaller to improve the quality of the printed image. For example, in the recent recording apparatus, ink of only 1 ng to 6 ng is jetted at a time to form a dot, while ink not less than 10 ng is jetted at a time to form a dot in the conventional recording apparatus. When the volume of ink jetted at a time is smaller, impression on a granular feature of the printed image may be improved, that is, the quality of the printed image may be improved.
However, at the same time, when the volume of ink jetted at a time is smaller, the viscosity of the ink in the nozzles is liable to increase. That is because the ink in the nozzles is used only little by little.
In the case, even when the stirring of the ink is carried out while the carriage is being accelerated, a first ink drop is liable to be jetted in a direction deviated from a normal direction. Consequently, the quality of the printed image may deteriorate.
Especially, when the area of the recording medium capable of being recorded in the width direction is enlarged, the time of scanning becomes longer. In the case, when a recording (jetting) operation starts at a position in the latter half of a line, the solvent of the ink is liable to evaporate more before the recording operation during the scanning operation. Consequently, the quality of the printed image may deteriorate worse, especially at the position where the recording operation has started.
SUMMARY OF THE INVENTION
The object of this invention is to solve the above problems, that is, to provide an ink-jet recording apparatus that can prevent viscosity of ink from increasing even when the volume of ink jetted at a time is smaller and even when an area of a recording medium capable of being recorded in a width direction thereof is enlarged.
In order to achieve the object, an ink-jet recording apparatus includes: a recording head having a nozzle; a micro-vibrating unit for causing ink in the nozzle to minutely vibrate; a recording-starting-position setting unit for setting recording-starting-position information that represents a position where the nozzle should start to jet the ink, according to recording data; a micro-vibrating-starting-position setting unit for setting micro-vibrating-starting-position information that represents a position where the micro-vibrating unit should start to cause the ink to minutely vibrate, according to the recording-starting-position information; a scanning-position-information outputting unit capable of outputting head-position information that represents a position of the recording head while the recording head is scanning; and a pre-recording micro-vibrating controlling unit for judging a micro-vibrating-starting timing according to the micro-vibrating-starting-position information and the head-position information in order to cause the micro-vibrating unit to operate.
According to the above feature, a meniscus of the ink in the nozzle may be caused to minutely vibrate for a predetermined time from a suitable timing (micro-vibrating-starting timing) just before an ink drop is jetted from the nozzle. Thus, the viscosity of the ink in the nozzle may be returned at a normal level just before the ink drop is jetted.
In order to achieve the object, another ink-jet recording apparatus includes: a recording head having a nozzle; a micro-vibrating unit for causing ink in the nozzle to minutely vibrate; a recording-starting-position setting unit for setting recording-starting-position information that represents a position where the nozzle should start to jet the ink, according to recording data; a micro-vibrating-ceasing-position setting unit for setting micro-vibrating-ceasing-position information that represents a position where the micro-vibrating unit should cease to cause the ink to minutely vibrate, according to the recording-starting-position information; a scanning-position-information outputting unit capable of outputting head-position information that represents a position of the recording head while the recording head is scanning; and a pre-recording micro-vibrating controlling unit for judging a micro-vibrating-ceasing timing according to the micro-vibrating-ceasing-position information and the head-position information in order to cause the micro-vibrating unit to stop.
According to the above feature, a meniscus of the ink in the nozzle may be caused to minutely vibrate till a suitable timing (micro-vibrating-ceasing timing) just before an ink drop is jetted from the nozzle. Thus, the viscosity of the ink in the nozzle may be kept at a normal level till the ink drop is jetted.
In order to achieve the object, another ink-jet recording apparatus inclu
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