Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-11-01
2004-05-25
Brooke, Michael S. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S014000
Reexamination Certificate
active
06739685
ABSTRACT:
This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2001-338022 filed in JAPAN on Nov. 2, 2001, which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a control method of causing an ink-jet head to eject ink by imparting energy to each of multiple ink chambers arranged adjoining the ink-jet head in accordance with image data as well as relating to an ink-jet printer for printing images using this control method.
(2) Description of the Prior Art
An ink-jet printer is a printer which prints images on recording media such as paper etc., by ejecting ink selectively from multiple ink chambers arranged adjoining an ink-jet head in accordance with image data, and is typically constructed such that, while a carriage having an ink-jet head mounted thereon is moved in the main scan direction perpendicular to the direction of conveyance of recording media, energy for causing ink to eject is applied to each of the ink chambers in accordance with image data. Such ink-jet heads can be categorized into two types, i.e., the thermal type which ejects ink by heating ink charged in ink chambers and the piezoelectric type which ejects ink by changing the volumes of ink chambers that hold ink therein.
The characteristics of a liquid ink used for image printing in ink-jet printers, such as viscosity and the like, are known to affect the ejection performance of ink from the ink chambers, having significant influence on the image forming conditions on the recording media and presenting sharp fluctuations depending on change in temperature. Therefore, to keep good print conditions of images on the recording sheet, temperature control of the ink-jet head is important.
Particularly, in thermal type ink-jet printers, since electric energy is imparted to each ink chamber of the ink-jet head and converted into thermal energy so as to heat the ink charged in the ink chamber, the ink ejection performance is liable to vary due to temperature rise of the whole ink-jet head. In addition to this, among the multiple ink chambers, some may be imparted with electric energy to eject ink, others may be imparted with no electric energy so as not to eject ink, resultantly a large difference in temperature occurs and hence produces fluctuations in ink ejection performance between the ejecting ink chambers and the non-ejecting ink chambers, lowering the image quality of printed images.
On the contrary, in piezoelectric type ink-jet printers in which piezoelectric elements are used to convert electric energy into mechanical energy so as to change the volumes of ink chambers, problems due to heat generation upon ink ejections, inherently, occur less often. However, among piezoelectric type ink-jet printers, there is a type that implements a so-called multi-drop printing process in which the tone of each pixel in the image is reproduced by up to seven serial ejections of ink as a maximum, for example, or with seven droplets of ink. With this type of ink-jet printer, as the frequency of electric energy applied to the ejecting ink chambers increases, generation of heat in the piezoelectric elements due to their deformation increases, hence causing the same problem as the thermal type ink-jet printers suffer, that is, temperature rise of the whole ink-jet head and increase in temperature difference between the ejecting ink chambers and the non-ejecting ink chambers, hence causing degradation of the image quality of printed images.
As a conventional ink-jet printer to deal with the above problems, Japanese Patent Application Laid-open Hei 3 No.246049 discloses a thermal type ink-jet printer configuration in which a certain amount of energy which will not cause ink ejection is applied to each of the non-ejecting ink chambers at the same time ink is ejected from ejecting ink chambers, so as to reduce the difference in ink temperature between the ejecting ink chambers and the non-ejecting ink chambers, keeping ink ejection performance uniform and preventing degradation of the image quality of printed images.
As another conventional example, Japanese Patent Application Disclosure Hei 11-511410 discloses a piezoelectric type ink-jet printer configuration in which drive pulses for heating are applied to each of non-ejecting ink chambers at the same time ink is ejected from ejecting ink chambers, so as to equalize the amount of heat generation from each ejecting ink chamber with that from each non-ejecting ink chamber, thereby keeping ink ejection performance uniform and preventing degradation of the image quality of printed images.
However, none of the conventional ink-jet printers including those disclosed in Japanese Patent Application Laid-open Hei 3 No.246049 and those disclosed in Japanese Patent Application Disclosure Hei 11-511410 have been manipulated so that when ink is ejected from the ink head, a specific amount of energy that can cause a temperature rise of the ink in the non-ejecting ink chambers equal to that of ink in the ejecting ink chambers can be imparted to each non-ejecting ink chamber. Therefore, in the conventional ink-jet heads, though energy is applied to each non-ejecting ink chamber at the same time ink is ejected from ejecting ink chambers, the temperatures of ink in all the ink chambers do not necessarily become equal, one to another, hence there still remains the problem of failure in reliably preventing the degradation of the image quality of printed images by uniformizing the ink ejection performance of all the ink chambers.
In sum, the ink in the ejecting ink chamber rises in temperature upon ejection of ink as it is heated by the difference between the quantity of heat generated by the input of energy for ejection and the quantity of heat carried away when the droplets of ink are ejected from the ejecting ink chamber. Accordingly, in order to cause ink in non-ejecting ink chambers to increase in temperature upon ejection of ink as much as the ink in the ejecting ink chambers and in order to make the ink in all the ink chambers arranged in the ink head substantially uniform in temperature, energy equivalent to the difference between the input of energy imparted to the ejection chamber and the quantity of energy carried away by the ink droplet should be imparted to each of the non-ejecting ink chambers.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a control method of an ink-jet head and an ink-jet printer with the ink-jet head, wherein, upon ejection of ink, an amount of energy, the difference obtained by subtracting the energy carried away by ejected ink droplets that are ejected to the outside, from the energy imparted to each ejecting ink chamber, can be imparted to each of the non-ejecting ink chambers, so that the temperature of ink charged in the ejecting ink chambers and the temperature of ink charged in the non-ejecting ink chambers will be equal, and, upon ejection of ink, the ink in non-ejecting ink chambers is elevated in temperature as much as the increase in temperature of the ink in ejecting ink chambers, whereby it is possible to make the ink ejection performance as to all ink chambers provided for the ink-jet head substantially uniform and positively prevent degradation of the image quality of printed images.
In order to achieve the above described object, the present invention is configured as follows.
In accordance with the first aspect of the present invention, a method of controlling an ink-jet head having a multiple number of ink chambers arranged adjacent thereto for forming images by selectively imparting energy to each of the ink chambers in accordance with image data so as to cause ink charged in the ink chambers to eject, is characterized in that an amount of energy U0, which is determined by
U
0=
Ui−Ud,
is imparted to each of non-ejecting ink chambers for one ink ejection cycle, where Ui is the energy to be imparted to each ejecting ink chamber that ejects ink, every ink ejection cycle, among the mul
Birch & Stewart Kolasch & Birch, LLP
Brooke Michael S.
Sharp Kabushiki Kaisha
LandOfFree
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