Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-03-02
2001-12-11
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06328402
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ink jet recording apparatuses, and more particularly, to an ink jet recording apparatus that can drive a piezoelectric element by applying a pulse voltage of a plurality of waveforms.
2. Description of the Related Art
Piezoelectric elements are conventionally used in the recording head of an ink jet printer. In such a recording head, the strain of the piezoelectric element driven by the applied voltage causes pressure to be applied to the ink within a predetermined closed cavity (ink channel). The ink is sprayed out towards a recording sheet from a nozzle provided in the ink channel in the form of ink droplets.
Ink droplets of a plurality of different size can be ejected by altering the level of the pulse amplitude of the rectangular pulse voltage applied to the piezoelectric element. Each ink droplet of various different size corresponds to a print dot diameter on the recording sheet. The half tone can be represented by controlling the magnitude of the pulse amplitude.
In such a printout by a rectangular pulse voltage, particularly in a printout of ink droplets of a greater diameter, various undesirable phenomena such as satellite (an ink droplet corresponding to a certain print dot diameter is sprayed out accompanying generation of a small ink droplet), dot split (the tip of the ink droplet sprayed out is split into two), curve (the direction of the ink droplet to be sprayed out is deviated) and the like are encountered. These phenomena of satellite, dot split, and curve become the cause of satellite dots, dot split noise, and ink hit position offset to significantly degrade the picture quality of the reproduced image.
Furthermore, in printout by means of a rectangular pulse voltage, particularly when the printout frequency which is the frequency of the pulse voltage to be applied is increased, similar undesirable phenomena such as satellite, dot split, and curve occurs. Thus, the picture quality of the image is significantly degraded by these phenomena.
Generation of a wave in the ink within the ink channel after an ink droplet is sprayed out towards a recording sheet is considered to be one cause of these phenomena of satellite, dot split, and curve. Although this wave is attenuated over time, application of a pulse voltage corresponding to the next ink droplet with the wave still occurring in the ink within the ink channel will cause the above-described satellite, dot split and curve phenomena.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide an ink jet recording apparatus that can represent half tone without reducing image quality.
Another object of the present invention is to provide an ink jet recording apparatus that can have the frequency for applying a pulse voltage increased.
A further object is to provide an ink jet recording apparatus that can improve image quality while offering a large dynamic range.
According to an aspect of the present invention, an ink jet recording apparatus includes a piezoelectric element to which a voltage is applied for generating a strain to spray out an ink droplet, a voltage generation device for applying a voltage to the piezoelectric element according to predetermined data, said voltage generation device generating a voltage of a waveform having a rising edge, a constant amplitude duration, and a controller for providing control so that the increase of voltage with respect to the time at the rising edge becomes smaller in proportion to a greater voltage at the amplitude duration.
According to another aspect of the present invention, an ink jet recording apparatus includes a piezoelectric element to which a voltage is applied for generating a strain to spray out an ink droplet, a voltage generation device for applying a voltage to the piezoelectric element according to predetermined data, said voltage generation device generating a voltage of a waveform having a rising edge, an amplitude duration, and a falling edge, and a controller for setting a voltage y at the end of the rise of the waveform of the voltage at time x so as to be on the curve of y=ax
n
where a is a constant and n is a positive constant smaller than 1, or the curve of x=a(0−sin&thgr;), y=b(1−cos&thgr;) where a and b are constants and &thgr; is a parameter.
According to a further aspect of the present invention, an ink jet recording apparatus includes a piezoelectric element to which a voltage is applied for generating a strain to spray out an ink droplet, a voltage generation device for applying a voltage to the piezoelectric element according to predetermined data, said voltage generation device generating a voltage of a waveform having a rising edge and a falling edge, and a controller for setting the time required for a fall to be longer than the time required for a rise.
According to still another aspect of the present invention, an ink jet recording apparatus includes an electromechanical conversion element to eject ink in an ink channel from a nozzle, a pulse apply unit to apply a pulse signal to the electromechanical conversion element, and a controller to control the pulse apply unit so that at least one of a rising speed and a falling speed of the pulse becomes lower as the amplitude of the pulse signal becomes greater.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5124716 (1992-06-01), Roy et al.
patent: 5170177 (1992-12-01), Stanley et al.
patent: 5461403 (1995-10-01), Wallace et al.
patent: 6-40031 (1994-02-01), None
patent: 6-171080 (1994-06-01), None
Barlow John
Minolta Co. , Ltd.
Sidley Austin Brown & Wood
Stephens Juanita
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