US 6,386,668 B1Granted

Ink jet recording apparatus

AssigneeToshiba Tec Kabushiki Kaisha

InventorsMegumi Shimizu, Atsushi Kubota, Hidehiro Watanabe, Takahisa Ikeda

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Abstract

In an ink jet recording apparatus having two head units, each having a large number of ink nozzles arranged in a line, assembled so that they overlap with each other, an 8-shade image signal is entered into a correction circuit and a line direction position signal is input into a position signal decision circuit. When the position signal decision circuit decides that the position signal represents the overlapping zone of the head units, the shade level of the image signal is divided between the head units. For example, when the shade level of the image signal is 7, one of the head units is allotted the shade level and the other is allotted the shade level. The overlapping nozzles in a pair eject droplets of ink to form one dot.

Claims14

Dependent claims

An ink jet recording apparatus comprising:

an ink jet head formed from a plurality of head units each having a large number of ink nozzles arranged in a line, the head units being arranged such that they are substantially parallel to one another in the direction of arrangement of their ink nozzles and, in the direction in which a recording medium moves, every two adjacent head units overlap with each other by a number Q of ink nozzles including a number P (Q>P>1) of ending ink nozzles that may cause a change in printing density;
and
drive means responsive to an input image signal for driving the ink jet head to cause selectively the ink nozzles to eject ink onto the recording medium for printing while moving the recording medium in a direction perpendicular to the line direction in which the ink nozzles of the respective head units are arranged;
wherein the driving means controls the ink jet head so that one dot is formed by ink ejection from each ink nozzle of one head unit in the overlapping zone of the adjacent head units and the corresponding one of the other head unit and the ratio in the amount of ejected ink of one to the other of overlapping ink nozzles is made variable so that the average printing density in the overlapping zone of the head units varies at a fixed rate;
and
wherein the amount of ejected ink from the one of the overlapping ink nozzles is smaller as it is closer to the end of its corresponding head unit.

3 more elements

An ink jet recording apparatus comprising:

an ink jet head formed from a plurality of head units each having a large number of ink nozzles arranged in a line, the head units being arranged such that they are substantially parallel to one another in the direction of arrangement of their ink nozzles and, in the direction in which a recording medium moves, every two adjacent head units overlap with each other by a number Q of ink nozzles including a number P (Q>P>1) of ending ink nozzles that may cause a change in printing density;
and
drive means responsive to an input image signal for driving the ink jet head to cause selectively the ink nozzles to eject ink onto the recording medium for printing while moving the recording medium in a direction perpendicular to the line direction in which the ink nozzles of the respective head units are arranged;
wherein the driving means controls the ink jet head so that one dot is formed by ink ejection from each ink nozzle of one head unit in the overlapping zone of the adjacent head units and the corresponding one of the other head unit and the ratio in the amount of ejected ink of one to the other of overlapping ink nozzles is made variable so that the average printing density in the overlapping zone of the head units varies at a fixed rate;
and ink nozzles including a number P (Q>P>1) of ending ink nozzles that may cause a change in printing density;
and
drive means responsive to an input image signal for driving the ink jet head to cause selectively the ink nozzles to eject ink onto the recording medium for printing while moving the recording medium in a direction perpendicular to the line direction in which the ink nozzles of the respective head units are arranged;
wherein the driving means controls the ink jet head so that one dot is formed by ink ejection from each ink nozzle of one head unit in the overlapping zone of the adjacent head units and the corresponding one of the other head unit and the ratio in the amount of ejected ink of one to the other of overlapping ink nozzles is made variable so that the average printing density in the overlapping zone of the head units varies at a fixed rate;
and
wherein the drive means includes:
decision means for deciding whether a line direction position signal represents the overlapping zone of first and second adjacent head units;
a table for storing first and second output shade levels of overlapping ink nozzles in the overlapping zone of the first and second head units, the first and second output shade levels being defined with respect to the line direction in which the ink nozzles are arranged and the paper feed direction perpendicular to the line direction for each of shade levels of the input image signal;
first and second shift registers connected with the table when the line direction position signal represents the overlapping zone of the first and second head units for having first and second output levels corresponding to a shade level of the input image signal set, respectively, from the table;
and
first and second driver circuits for driving the first and second head units, respectively, in accordance with the first and second output levels set in the first and second shift registers.

12 more elements

An ink jet recording apparatus comprising:

an ink jet head formed from a plurality of head units each having a large number of ink nozzles arranged in a line, the head units being arranged such that they are substantially parallel to one another in the direction of arrangement of their ink nozzles and, in the direction in which a recording medium moves, every two adjacent head units overlap with each other by a number Q of one another in the direction of arrangement of their ink nozzles and, in the direction in which a recording medium moves, every two adjacent head units overlap with each other by a number Q of ink nozzles including a number P (Q>P>1) of ending ink nozzles that may cause a change in printing density;
and
drive means responsive to an input image signal for driving the ink jet head to cause selectively the ink nozzles to eject ink onto the recording medium for printing while moving the recording medium in a direction perpendicular to the line direction in which the ink nozzles of the respective head units are arranged;
wherein the driving means controls the ink jet head so that one dot is formed by ink ejection from each ink nozzle of one head unit in the overlapping zone of the adjacent head units and ink ejection from the corresponding one of the other head unit and the ratio in the amount of ejected ink of one to the other of overlapping ink nozzles is made variable so that the average printing density in the overlapping zone of the head units is made substantially equal to the average density in the non-overlapping zones;
and
wherein the drive means includes:
decision means for deciding whether a line direction position signal represents the overlapping zone of first and second adjacent head units;
a table for storing first and second output shade levels of overlapping ink nozzles in the overlapping zone of the first and second head units, the first and second output shade levels being defined with respect to the line direction for each of shade levels of the input image signal;
first and second shift registers connected with the table when the line direction position signal represents the overlapping zone of the first and second head units for having first and second output levels corresponding to a shade level of the input image signal set, respectively, from the table;
and
first and second driver circuits for driving the first and second head units, respectively, in accordance with the first and second output levels set in the first and second shift registers.

8 more elements

An ink jet recording apparatus comprising:

an ink jet head formed from a plurality of head units each having a large number of ink nozzles arranged in a line, the head units being arranged such that they are substantially parallel to one another in the direction of arrangement of their ink nozzles and, in the direction in which a recording medium moves, every two adjacent head units overlap with each other by a number Q of ink nozzles including a number P (Q>P>1) of ending ink nozzles that may cause a change in printing density;
and
drive means responsive to an input image signal for driving the ink jet head to cause selectively the ink nozzles to eject ink onto the recording medium for printing while moving the recording medium in a direction perpendicular to the line direction in which the ink nozzles of the respective head units are arranged;
wherein the driving means controls the ink jet head so that one dot is formed by ink ejection from each ink nozzle of one head unit in the overlapping zone of the adjacent head units and ink ejection from the corresponding one of the other head unit and the ratio in the amount of ejected ink of one to the other of overlapping ink nozzles is made variable so that the average printing density in the overlapping zone of the head units is made substantially equal to the average density in the non-overlapping zones;
and
wherein the drive means includes:
decision means for deciding whether a line direction position signal represents the overlapping zone of first and second adjacent head units;
a table for storing first and second output shade levels of overlapping ink nozzles in the overlapping zone of the first and second head units, the first and second output shade levels being defined with respect to the line direction in which the ink nozzles are arranged and the paper feed direction perpendicular to the line direction for each of shade levels of the input image signal;
first and second shift registers connected with the table when the line direction position signal represents the overlapping zone of the first and second head units for having first and second output levels corresponding to a shade level of the input image signal set, respectively, from the table;
and
first and second driver circuits for driving the first and second head units, respectively, in accordance with the first and second output levels set in the first and second shift registers.

8 more elements

Dependencies are inferred from the claim text.