Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-09-22
2001-12-18
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S010000, C347S048000
Reexamination Certificate
active
06331052
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet printing apparatus, and more particularly, to an ink jet printing apparatus provided with an ink jet head including a plurality of nozzles.
2. Discussion of the Related Art
In the ink jet printing apparatus provided in a printer, a facsimile device, a copying machine, etc., an ink drop is ejected from a selected nozzle by driving the energy generating medium of the ink jet head in accordance with the printing data by use of an ink jet head provided with a plurality of nozzles for ejecting ink drops, an ink chamber communicating with the respective nozzles, and energy generating media (energy generating elements) such as electromechanical conversion elements or electrothermal conversion elements for generating energy in order to pressurize ink in the respective ink chambers and thereby eject ink drops from the nozzles.
In the present specification, “to drive the energy generating medium” is also referred to as “to drive the nozzle” or “to drive the channel”.
When ejecting an ink drop from a selected or designated nozzle, the meniscus of an adjacent non-ejection nozzle which is at that time prohibited from ejecting an ink drop (called “non-drive nozzle”) is put in an unstable state by the mechanical or fluid interference.
As a result, the ink ejection speed Vj and the ink ejection amount Mj vary. In the end, air enters the ink chamber through the nozzle of the non-ejection nozzle. Furthermore, in the case of a “non-drive nozzle” being surrounded by two nozzles on either side of the “non-drive nozzle” which are “ejection nozzles” or “drive nozzles” for ejecting an ink drop, the energy generating medium of the two drive nozzles pressurizes the ink chamber and thereby the nozzle forming member of the non-drive nozzle is slightly pushed up. For this reason, the inner volume of the ink chamber of the non-drive nozzle is slightly increased, and thereby, the ink meniscus of the non-drive nozzle is pulled toward the inside of the non-drive nozzle. If such a phenomenon occurs successively, air is accumulated in the ink chamber of the non-drive nozzle.
When the air is accumulated in the ink chamber of the non-drive nozzle in such a way, even though the ink chamber of the non-drive nozzle is pressurized by the energy generating medium, after the non-drive nozzle has been changed to a drive nozzle, the ink drop may not be ejected. As a result, the image quality is lowered and the printing results deteriorate.
In the prior art, there are many methods of driving ink jet print heads. For instance, as described in the published specification of Japanese Laid-open Patent Publication No. 58-203/1983, an ink jet printing head includes adjacent ink chambers and nozzles. In order to make an ink ejection speed uniform in all cases, when one of the pressure chambers is pressurized to thereby eject an ink drop therefrom, the other adjacent pressure chamber is pressurized to a level such that an ink drop is not ejected.
In another prior art device described in the published specification of Japanese Laid-open Patent Publication No. 6-8428/1994, an ink jet printing apparatus includes a pulse signal outputting medium for outputting signals having different pulse widths in synchronism with the drive signal and a signal selection medium for selecting one signal from the output signals. The ON-OFF state of the piezoelectric element driving medium is changed even in the unsaturated area of the drive signal. As a result, the voltage applied to the piezoelectric element is changed so as to make constant the amount of the ink in each ink drop ejected from the respective nozzles. Such a method of driving is well known.
Furthermore, in the ink jet printing apparatus in which plural signals respectively having different pulse widths in synchronism with the drive signal are output and the applied voltage is changed by selecting one signal from the plural signals and changing the state of the drive media for charging the respective piezoelectric elements from “on” to “off”, if the turn-off time of the transistors becomes uneven, the applied voltage also becomes uneven. As a result, the applied voltage cannot be controlled with high precision.
SUMMARY OF THE INVENTION
To overcome the above-mentioned problems in the prior art, the preferred embodiments of the present invention provide an ink jet printing apparatus capable of reliably and accurately ejecting an ink drop to thereby produce an image of exceptionally high quality.
According to a preferred embodiment of the present invention, an ink jet printing apparatus includes an ink jet head, having a plurality of nozzles for respectively ejecting ink drops, a plurality of ink chambers communicating with the plurality of nozzles, and a plurality of electromechanical conversion elements corresponding to the respective nozzles, wherein a volume inside of the ink chamber is changed by driving the electromechanical conversion elements in order to eject the ink drops from the respective nozzles and a non-ejection driving waveform having drive energy to an extent of not ejecting the ink drops is applied to all of the electromechanical conversion elements of the non-drive nozzles not ejecting any ink drops when the electromechanical conversion elements of the ink jet head are driven in accordance with the image data.
By applying the non-drive energy or waveform to the non-drive electromechanical conversion elements corresponding to the non-drive nozzles, an increase in the ink chambers of the non-drive nozzles is cancelled and problems with mis-ejection or insufficient ejection of ink drops are prevented and accurate and high quality images are produced.
According to another preferred embodiment of the present invention, the ink jet printing apparatus described above includes a medium for transmitting data for driving the electromechanical conversion elements of the non-drive nozzles such that drive energy set for not ejecting the ink drive is applied by restricting a drive voltage of the drive waveform which is applied to the electromechanical conversion elements of drive elements for ejecting an ink drop. As a result, the reduced drive energy restricted as described above to a level such that ink drops are not ejected is applied to the electromechanical conversion elements of the non-drive nozzles by a significantly simplified structure.
According to another preferred embodiment of the present invention, the ink jet printing apparatus described above is constructed such that when the electromechanical conversion element is driven in accordance with the image data, the drive energy set for not ejecting an ink drop is applied to the electromechanical conversion element of a specified non-drive nozzle. As a result, a volume increase in the ink chamber of the non-drive nozzle is cancelled and consequently, an undesirable ink jet mis-ejection or insufficient ejection due to sucking of air is prevented. This ink jet printing apparatus, therefore, accurately and reliably produces excellent image quality and significantly reduces power consumption and ink dot migration.
Other features, advantages and beneficial characteristics of the present invention will become more apparent from the detailed description of preferred embodiments thereof which will be described below with reference to the attached drawings.
REFERENCES:
patent: 5204695 (1993-04-01), Tokunaga et al.
patent: 5499042 (1996-03-01), Yanagawa
patent: 5831650 (1998-11-01), Reinten
patent: 5923351 (1999-07-01), Hosono et al.
patent: 6053596 (2000-04-01), Nakano et al.
Fujii Mitsumi
Hirota Tetsuro
Kakuda Shinichi
Makita Hideyuki
Matsumoto Shuzo
Barlow John
Do An H.
Ricoh & Company, Ltd.
Traurig LLP Greenberg
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