Patent ID: 8801132
Filing Date: 2014-08-12
Classification: B41J

Abstract:
1. An inkjet printer in which ink dot sizes on a medium are modulated in plural levels to perform multi-gradation printing, the printer comprising: an inkjet head including nozzles for ejecting ink droplets while the inject head is moving in a line direction relative to the medium; and an ejection control section for controlling ejection of the ink droplets from the nozzles by providing ejection control signals to the nozzles; wherein the inkjet head forms dot lines in a direction perpendicular to the line direction in a juxtaposed manner in which the ink dots are juxtaposed in the line direction; wherein the inkjet head forms dots of the same color by ejecting the ink droplets from one of the nozzles corresponding to a respective dot line in each of the dot lines; wherein, when one of the ink droplets is ejected from the one of the nozzles, the ejection control section provides one of the ejection control signals corresponding to an ink dot size for the one of the nozzles, and the one of the nozzles ejects the ink droplet corresponding to the one of the ejection control signals from the ejection control section to provide an ink dot having the ink dot size corresponding to the one of the ejection control signals; wherein the ejection control section changes control of the ejection of the ink droplets depending on whether one of the nozzles for forming the respective dot line is an abnormal nozzle, which is characterize by an ejection error representing a difference between a volume of the ink droplet ejected and a predetermined standard value selected from a permitted range, or the election control section changes control of the ejection of the ink droplets depending on whether one of the nozzles for forming the respective dot line is a normal nozzle, which is characterized by an ejection error within the permitted range; wherein the ejection control section supplies the abnormal nozzle an ejection control signal corresponding to an ink dot size for a part of the ink dots juxtaposed in the respective line different from the ejection control signal supplied for an ink dot size for a part of the ink dots juxtaposed in the respective line for the normal nozzle; and wherein the ejection control section supplies the abnormal nozzle an ejection control signal different from the ejection control signal for the normal nozzle that is characterized by an average value in the respective dot line of the ejection errors that is minimized close to zero in comparison with a case that the ejection control signal for the normal nozzle is supplied as the ejection control signal corresponding to all of the ink dots in the respective dot line.