Incremental printing of symbolic information – Ink jet – Controller
Utility Patent
1998-09-28
2001-01-02
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S014000, C347S019000, C201S001000
Utility Patent
active
06168252
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet printer having a printhead where when a piezoelectric element receives a drive voltage, the piezoelectric element is deformed to eject ink drops.
2. Description of the Related Art
Conventional ink jet printers suffer from a problem that the properties of the ink such as viscosity change with environmental changes. Changes in ink property cause poor print quality. Viscosity of ink is high at low temperatures, causing smaller ink drops. Conversely, viscosity is low at higher temperatures, causing larger ink drops.
At the same temperature, lower drive voltages cause smaller shear mode deformation of the piezoelectric element, resulting in lower pressures in the ink pressure chamber formed of the piezoelectric element. As a result, ink drops ejected from the ink chamber are small. Conversely, higher drive voltages cause larger shear mode deformation of the piezoelectric element, resulting in higher pressures in the pressure chamber. The higher pressures cause larger ink drops.
Therefore, variations in the size of ink drop due to temperature variations can be compensated for by increasing the drive voltage when the temperature is relatively low, and decreasing when the temperature is relatively high.
With some conventional printers, the temperatures of environment, printhead, or ink are measured and the drive conditions of the printhead are controlled in accordance with the measured temperature, thereby maintaining the same print quality. If a printhead is formed of a piezoelectric material whose dielectric constant is a function of temperature, the temperature of the printhead can be determined in terms of capacitance. Then, drive conditions are adjusted in accordance with the property of ink at the measured temperature. This way of temperature compensation is effective since the capacitance of the piezoelectric element is substantially proportional to the temperature.
However, even at the same temperature, the capacitance value of the piezoelectric element may vary from printhead to printhead. Different capacitances are interpreted as different temperatures of the printheads. Thus, if the drive conditions of the printhead are to be adjusted in accordance with the capacitance of the printhead, the printheads are driven under different drive conditions at the same temperature. Thus, ejected ink drops are of different sizes, causing poor print quality.
SUMMARY OF THE INVENTION
An object of the invention is to provide a printer having a printhead which ejects ink drops of the same size regardless of the temperature of the printhead.
Another object of the invention is to provide a printer having a printhead which ejects ink drops of the same size regardless of changes in the viscosity of ink with temperature.
An ink jet printer has a printhead formed of a piezoelectric element having a capacitance whose value is a function of the temperature of the printhead. The piezoelectric element is deformed to eject ink drops from the printhead in accordance with drive voltages applied to the piezoelectric element.
A memory stores a reference temperature Tref of the printhead and a reference capacitance Cref of the printhead measured at the reference temperature Tref.
A capacitance measuring section measures a value Cm of the capacitance of the printhead at a value Te of the temperature of the printhead. A temperature computing section
22
computes the first value Te of the temperature on the basis of the reference capacitance Cref, the temperature Tref, and the measured second capacitance value Cm. A temperature-drive voltage table lists values of the temperature Te and corresponding values of the drive voltages. A voltage selecting section selects an optimum value of drive voltage from among the values of the drive voltage listed in the temperature-voltage table. The optimum value is a value corresponding to a temperature which is the closest to the computed temperature. The optimum value is used to drive the printhead.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4614567 (1986-09-01), Stahlherm et al.
patent: 6050665 (2000-04-01), Kishi
patent: 6062668 (2000-05-01), Cruz-Uribe
Akin Gump Strauss Hauer & Feld L.L.P.
Barlow John
Lago Cesar G.
Oki Data Corporation
LandOfFree
Ink jet printer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet printer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet printer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2528533