Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-02-05
2001-09-18
Tran, Huan (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S010000, C347S011000
Reexamination Certificate
active
06290317
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an inkjet printing apparatus, and in particular, to an inkjet printing apparatus which prints an image by discharging an ink drop by means of a piezoelectric element.
BACKGROUND OF THE INVENTION
Conventionally, there are known inkjet printers having print heads provided with a piezoelectric element (PZT).
For such print heads, a pulse voltage corresponding to image information is applied to the piezoelectric element, causing a predetermined distortion of the piezoelectric element. This distortion pressurizes ink inside an adjacent container, or ink channel, and an ink drop is discharged from the ink channel toward a print sheet, thus forming a printed ink dot. A plurality of printed ink dots yields an image on the print sheet.
In the inkjet printers described above, a distortion of a varied magnitude is generated in the piezoelectric element by varying the pulse amplitude (intensity) of the applied pulse voltage. The quantity of ink discharged from the nozzle is determined by the magnitude of the applied pulse voltage. Consequently, by adjusting the quantity of ink within an ink drop, a plurality of printed ink dot diameters can be obtained. For purposes of printing, varying ink dot diameters allows image tones to be expressed, for example, a large diameter ink drop expresses dark portions of an image, while a small diameter ink drop expresses light portions of an image.
FIGS. 13 and 14
are graphs showing examples of waveforms of a series of pulse voltages applied to piezoelectric elements of an inkjet printer print head for the purpose of discharging ink.
FIG. 13
illustrates a series of pulse voltages having a set amplitude from between 5 V to 50 V. Consequently, application of such pulse voltages to a print head, being constructed in a manner consistent with the above description, would result in ink drops having different volumes being discharged, wherein the volume of an ink drop is proportional to the pulse amplitude of its generating pulse.
Similarly,
FIG. 14
illustrates a series of pulse voltages having a set amplitude from between 5 V to 50 V. Ink drops of different sizes, i.e., volumes, would be formed and discharged in accordance with these applied pulse amplitudes, thereby producing printed ink dots of different diameters on a print sheet. Note that, the rising portions of the 5 V and 10 V pulse voltages are steeper than the remaining pulse voltages. The steeper rising portions are used to suppress variations in printed ink dot shape by increasing the discharge velocities of the ink drops.
As shown in
FIGS. 13 and 14
, high amplitude voltage pulse voltages are necessary to provide a full range of printed ink dot diameters. Consequently, a power source, an amplifier, a switching IC, and so forth used for an electric circuit for generating such pulse voltages are required to have high voltage ratings, large capacities, and high responsivity. Understandably, these requirements cause increased production costs, increased circuit size, and the like.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming the problems described above. According to one embodiment of the present invention, an inkjet printing apparatus is disclosed for producing half-tone images on a print sheet in accordance with input image data. The inkjet printing apparatus forms such images by discharging ink from a print head. The inkjet printing apparatus according to the present invention includes at least one ink chamber, suitable for storing ink, having a flexible wall which defines a portion of the ink chamber; at least one piezoelectric element contacting the flexible wall of the at least one ink chamber; and a driver to drive the at least one piezoelectric element in accordance with input image data. The driver applies a drive voltage having a pulse width corresponding to a desired tone of the input image data.
With particular regard to the at least one piezoelectric element, it has a first surface contacting the flexible wall of the at least one ink chamber. The at least one piezoelectric element is also polarized in a polarized direction, the polarized direction being perpendicular to the flexible wall of the at least one ink chamber. For deformation of the at least one piezoelectric element, the drive voltage is applied to the piezoelectric element in a direction parallel to said polarized direction, and said piezoelectric element deforms in the polarized direction in response to an applied drive voltage.
A method of forming a half-tone image using such apparatus could involve applying a first pulse voltage to a piezoelectric element head to thus discharge an ink drop to form a printed ink dot having a first diameter, the first pulse voltage having a first waveform including a first rising interval, a first pulse amplitude duration interval at a first pulse amplitude, and a first falling interval, and applying a second pulse voltage to a piezoelectric element to thus discharge an ink drop to form a printed ink dot having a second diameter, the second diameter being greater than the first diameter, the second pulse voltage having a second waveform including a second rising interval, a second pulse amplitude duration interval at a second pulse amplitude, and a second falling interval.
For the second diameter of a second printed ink dot to be greater than the first diameter of a first printed ink dot, a variety of modifications may be made with respect to the waveforms of the first and second pulse voltages. For example, a slope of the second falling interval may be made greater than a slope of the first falling interval; the second pulse amplitude duration interval may extend longer than the first pulse amplitude duration; or a slope of the first rising interval may be made greater than a slope of the second rising interval.
An object of the present invention is to provide an inkjet printing apparatus capable of reducing both the size of a circuit for printing an image and production cost, maintaining printing performance and quality.
Other objects and advantages of the present invention will be apparent to those of ordinary skill in the art having reference to the following specification together with the drawings.
REFERENCES:
patent: 4521786 (1985-06-01), Bain
patent: 4561025 (1985-12-01), Tsuzuki
patent: 4980699 (1990-12-01), Tanabe et al.
patent: 5402159 (1995-03-01), Takahashi
patent: 5461403 (1995-10-01), Wallace
patent: 5471231 (1995-11-01), Hiraishi
patent: 5552809 (1996-09-01), Hosano
patent: 5557304 (1996-09-01), Stortz
patent: 5639508 (1997-06-01), Okawa et al.
patent: 5943079 (1999-08-01), Yoshida
patent: 6024438 (2000-02-01), Koike et al.
patent: 0437062 (1991-07-01), None
patent: 6-182998 (1994-07-01), None
Do An H.
Minolta Co. , Ltd.
Sidley Austin Brown & Wood
Tran Huan
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