Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-06-11
2001-09-18
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S005000
Reexamination Certificate
active
06290325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control method for an ink jet printer whereby characters expressed using dot matrices are printed using a print head that has plural nozzles and moves parallel to the printed line, and relates particularly to a method for generating preliminary ejection data according to which ink is ejected from the nozzles to refresh the print head.
2. Description of the Related Art
In general, conventional ink jet printers print to a recording medium by writing the image signal into memory or other storage means, and then selectively driving pressure-inducing means such as piezoelectric elements or heat-emitting elements proximal to the nozzles based on the image signal.
A nozzle purging process is also commonly used in addition to this printing process. This purging process regularly ejects ink droplets from all nozzles to prevent nozzle clogging and maintain printer performance.
This purging process is referred to as a preliminary ejecting process and is described in Japanese patent laid-open specification number H3-292148 (1991292148). More specifically, Japanese specification H3-292148 describes an ink jet printer comprising a selector for selecting either image data transferred to the printer or the preliminary ejection data generated by a preliminary ejection data generating circuit. This ink jet printer accomplishes either the normal print process or a preliminary ejecting process by writing to memory the data selected according to the selection signal and outputting the stored data to the ink jet head through a head driver.
The problems with this conventional method are described below. (1) The preliminary ejection data generated by the preliminary ejection data generator is written to memory in the same manner as the image data. It is therefore necessary to write the preliminary ejection data to memory for every preliminary ejecting process. This complicates the process and degrades the image data transfer efficiency if the preliminary ejecting process is frequently executed because of the increased frequency of the data transfer interrupts and memory writing operations required to execute each preliminary ejecting process. More specifically, this results in an overall reduction in the printing speed because image data cannot be received by the printer during the preliminary ejecting process. (2) Because the preliminary ejection data generated by the preliminary ejection data generator is written to memory in the same manner as the image data, the printing process is interrupted and the preliminary ejection data is written to memory every time the preliminary ejecting process is executed. This makes it necessary to delete the image data already stored in memory. To then resume the normal printing process after the preliminary ejecting process, the deleted image data must be written to memory again. This again complicates the process, degrades the image data transfer efficiency, and results in an overall reduction in the printing speed. (3) While problems (1) and (2) above can be resolved by increasing the available memory, this also increases the cost. With the popularization of color ink jet printers and high resolution multi-nozzle ink jet printers in recent years, the costs associated with increasing the on-board memory are significant. (4) In order to increase the dot density and thereby increase print quality, ink jet printers having an inclined nozzle row in the scanning direction have been proposed, thereby effectively reducing the vertical pitch between the recording dots. When using an ink jet head in which the nozzles are thus diagonally arrayed, however, both the column print data received by the printer and the preliminary ejection data must be converted to diagonally arrayed print data, thus further degrading the printing speed.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to resolve the above problems by enabling the preliminary ejection data to be output to the print head whether or not image data is being transferred to the printer during the preliminary ejecting process, and to thereby improve the throughput of the printing process.
To achieve the above objects an ink jet printer having plural print elements for ejecting ink droplets and a print head for printing while moving relative to the print medium comprises a print pattern storage means for storing the input data and sequentially outputting the stored data in conjunction with the relative movement of the print head, a preliminary ejection data generator for causing ink droplets to be ejected simultaneously from plural print elements of the print head, and a selecting means for selecting the output from either the print pattern storage means or the preliminary ejection data generator, and ejecting ink droplets from the plural print elements according to the selected output.
As a result of this configuration, the preliminary ejecting process can be executed without writing and storing the preliminary ejection data in the print pattern storage means. It is therefore possible to write and store only the image data in the print pattern storage means, and there is no decrease in the image data transfer performance as a result of the preliminary ejecting process. Furthermore, because the preliminary ejection data is not stored in the print pattern storage means, the time required for the preliminary ejecting process itself is reduced, and the total printing speed including the preliminary ejecting process can therefore be improved. It is also not necessary to store the preliminary ejection data in large sized RAM, making it possible to achieve a high speed preliminary ejecting process and printing with minimal RAM, and thus making it possible to provide a high cost performance printer.
The print pattern storage means can comprise a RAM, but it is also possible to provide plural shift registers for each print element, allocate the input data to each of the print elements, and store the data in the corresponding shift registers. This makes it possible by shifting the data stored in the shift registers synchronized to the relative movement of the print head to output the data to the print elements without overloading the CPU while using a simple circuit configuration.
The ink jet printer of the present invention may also array any two of the plural print elements of the print head such that the line between those two print elements is not perpendicular to the relative direction of print head movement, and said ink jet printer further comprises a non-perpendicular array print pattern generator for converting the print pattern stored in the print pattern storage means to a pattern corresponding to the non-perpendicular arrangement of the plural print elements.
By means of this configuration it is not necessary to convert the preliminary ejection data to non-perpendicular array print data even if the print elements are arrayed non-perpendicularly to the print line, and the speed of the printing process can therefore be improved.
The image data stored to the print pattern storage means may also be either normal bit-mapped image data or rasterized image data, but when rasterized image data for a serial printer is received in line units, the image data must be converted to column-unit image data corresponding to vertically arrayed print elements. It is not necessary in this case to convert the preliminary ejection data to column-unit data, and the speed of the printing process can therefore be improved.
The drive method for an ink jet printer having plural print elements for ejecting ink droplets and a print head for printing while moving relative to the print medium is characterized by a printing process for storing the input data in the print pattern storage means, reading the data stored in the print pattern storage means in conjunction with the relative movement of the print head, and selectively ejecting ink droplets from each of the print elements according to said data, and a preliminary ejecting proc
Hanamura Makoto
Kobayashi Naoki
Minowa Masahiro
Seiko Epson Corporation
Tran Huan
LandOfFree
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