Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-07-22
2002-03-19
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S009000, C347S011000
Reexamination Certificate
active
06357846
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus and an ink jet recording method using the same. More particularly, the present invention relates to an ink jet recording apparatus and an ink jet recording method using the same, which prevents an increase of a viscosity of the ink in each nozzle of the recording head by vibrating the ink meniscus to such an extent as not to eject an ink drop.
As well known, the ink jet printer is provided with a recording head having a number of nozzles arrayed in a subscanning direction (vertical direction). To print, the recording head is moved in a main scanning direction (horizontal direction) by a carriage mechanism, and a printing medium, e.g., a printing paper, is fed or moved in the subscanning direction. The printer receives print data from a host computer connected thereto, develops the print data into dot pattern data, and drives the recording head, in accordance with the dot pattern data, to eject ink drops through orifices of the nozzles of the recording head at predetermined timings. Those ink drops land on a printing medium, such as a printing paper or an OHP sheet, to print characters, graphical objects and others on the printing medium.
To prevent ink bleeding, it is desirable that the ink drop is quickly dried and solidified. To this end, the ink is generally prepared so that its ink solvent quickly evaporates. It is a rare case that ink drops are ejected through all the nozzle orifices. In most cases, the recording head ejects ink drops toward predetermined or selected positions on the printing medium during a main scanning operation. Accordingly, each main scanning period includes ink ejection periods to eject ink drops and non-ejection periods to eject no ink drops. During the non-ejection period, each nozzle allows water to evaporate from the ink through its orifice, so that a viscosity of the ink increases (referred to frequently as a viscosity increase). The nozzles located at the top and bottom positions on the head face of the recording head are infrequently used when comparing with those nozzles located in the central portion on the head face. Therefore, in the top and bottom nozzles the non-ejection period is long, and those nozzles frequently suffer from the viscosity increase. The viscosity increase brings about many problems: the flying performance of the ejected ink drop is unstable, the nozzle is clogged with dried ink, and the print quality is deteriorated.
To prevent the nozzle clogging, the recording head is usually flushed under predetermined conditions. Specifically, the following operation is periodically performed. The recording head is retracted to a cleaning region, small amounts of ink drops are forcibly discharged from all the nozzles to refresh the ink located near the nozzle orifices.
When the recording head is flushed, the ink near the nozzle orifices is forcibly replaced with fresh ink. In this case, the forcibly discharged ink is wasted, leading to increase of print cost. Further, the flushing operation inevitably interrupts the printing operation. The interruption of the printing operation decreases the printing speed per page, and hence increases of the print time. In recent years, the color printing is widely used. In the circumstances, the nozzles of each color inevitably suffer from the viscosity increase problem.
A technique to refresh the ink near the nozzle orifice by finely vibrating the meniscus of ink during the main scanning operation as well as to forcibly discharge the ink is disclosed in Japanese Patent Publication 57-61576A, for example. To refresh the ink near the nozzle orifice, the technique applies fine pulse signals to the piezoelectric vibrators during the main scanning operation, to thereby finely vibrate the meniscus to such an extent as not to discharge the ink drop. Hereinafter, “fine vibration” means vibration whose amplitude do not eject ink from the nozzle orifices.
As described above, the related technique vibrates the meniscus to prevent the ink viscosity thereof from increasing. However, frequent operations of vibrating the meniscus urges the solvent of the ink to evaporate, possibly resulting in an increase of ink viscosity. Some time elapses till the vibration of the meniscus damps and the vibrating meniscus settles down. If the meniscus is finely vibrated just before an ink drop is ejected, the quantity, shape and a flying path of the ink drop will vary, deteriorating the print quality. The fine vibration influence on a viscosity of ink near the nozzle orifice depends on ambient temperature, aging of the ink and other factors. Application of a uniform fine vibration to the meniscus in circumstances where various related parameters vary from moment to moment will entail an excessive vibration of the meniscus. The excessive vibration leads to increase of the ink viscosity. Thus, it is safe to say that the related technique lacks relationships between the meniscus and the operating conditions of the nozzles (ink drop ejection time and position), ambient conditions and the like, and hence the related technique succeeds in presenting an insufficient solution to the viscosity increase problem.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method using the same which is free from the viscosity increase problem, and stabilizes a flying path of an ink drop ejected, with a unique and novel technical idea that the meniscus of ink in each nozzle is finely vibrated under the control based on the operating conditions of each nozzle.
To achieve the above object, an ink jet recording apparatus of the present invention is arranged such that operating conditions of each nozzle are analyzed in advance, and necessary fine vibration is applied to the meniscus of ink in each nozzle at necessary positions.
In order to achieve the above object, there is provided an ink jet recording apparatus comprising: a recording head provided with nozzles each from which an ink drop is ejected by operating associated pressure generating elements in accordance with inputted print data; driving signal generating means for generating a first driving signal and a second driving signal, the first driving signal for operating the pressure generating element so as to eject the ink drop, the second driving signal for operating the pressure generating element such an extent as to not eject the ink drop; data generating means for selecting at least one predetermined operation pattern for operating the pressure generating element in accordance with operating condition of each nozzle analyzed with reference to the print data in order to generate a dot pattern data in which the first and second data are arranged in accordance with the selected pattern; and switching means for inputting the first and second driving signals to the pressure generating element in accordance with the dot pattern data for each printing period.
The “pressure generating element” is an element capable of varying a pressure of ink in accordance with an input signal applied thereto, and is preferably a piezoelectric element which expands and contracts in accordance with an input signal. A heat generating element, which generates air bubbles when it is heated and varies a pressure of ink by the generated bubbles, may be used for the pressure generating element. The “second driving signal” may be a signal capable of finely vibrating the meniscus of ink to such an extent as to not eject an ink drop through the nozzle. It may take various energy levels and variation forms. The first and second data are typically expressed in terms of “1” or “0”. When “1” is set to the print bit data (print bit data is made valid), the ink drop is ejected. When “0” is set to the first data (first data is made invalid), the ink drop is not ejected. When the second data is valid, a fine vibration is applied to the meniscus of ink (i.e., the meniscus is finely vibrated). When the second data is invalid, a fine vibration is n
Barlow John
Do An H.
Seiko Epson Corporation
Sughrue & Mion, PLLC
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