Patent ID: 7452045
Filing Date: 2008-11-18
Classification: B41J

Abstract:
1. An ink-jet recording apparatus comprising: an ink-jet head having a passage unit in which formed are a plurality of individual ink passages each extending from an exit of a common ink chamber through a pressure chamber to a nozzle, and an ejection energy applier which applies ink ejection energy to ink contained in the pressure chamber; a conveyance mechanism which moves a recording medium relative to the ink-jet head; a waveform signal output circuit which selectively outputs, to the ejection energy applier unit, either one of a first waveform signal including a pulse for driving the energy applier so as to make an ink droplet ejected from the nozzle and a second waveform signal including a pulse for driving the ejection energy applier so as not to make an ink droplet ejected from the nozzle; a continuous non-ejection counter which counts, for each nozzle, a continuous non-ejection number which means the number of printing cycles during which non-ejection of an ink droplet from the nozzle continues until a latest printing cycle, where a printing cycle is a time required for a relative movement of the recording medium by a unit distance which corresponds to a printing resolution of an image to be formed; an ejection history memory which stores therein, for each nozzle, an ejection history of whether an ink droplet has been ejected from the nozzle or not in each of a predetermined number of continuous printing cycles up to the latest printing cycle; a non-ejection frequency detector which detects, for each nozzle, a non-ejection frequency which corresponds to an occurrence pattern of, in the ejection history stored in the ejection history memory, the printing cycle during which an ink droplet has not been ejected from the nozzle; a thickening degree determiner which determines, for each nozzle, a thickening degree of ink in the nozzle based on the continuous non-ejection number counted by the continuous non-ejection counter and the non-ejection frequency detected by the non-ejection frequency detector; and a waveform signal selector which makes the waveform signal output circuit output the second waveform signal to the ejection energy applier corresponding to a nozzle, when an ink droplet is not ejected from the nozzle in the current printing cycle and in addition a thickening degree in the nozzle determined by the thickening degree determiner is equal to or greater than a predetermined value.