Patent ID: 8678531
Filing Date: 2014-03-25
Classification: B41J

Abstract:
1. A driving apparatus of an inkjet head having a plurality of pressure chambers arranged in parallel and partitioned by partition walls made of a piezoelectric material, each of the partition walls being sandwiched between a plurality of electrodes arranged on the partition walls, each pressure chamber in fluid communication with a nozzle from which ink is ejected, each partition wall sandwiched between the electrodes forming an actuator shared by two pressure chambers which are in contact with the partition wall, the driving apparatus comprising: a drive signal output unit which outputs to the actuator a drive signal including ejection pulses that are used to generate pressure oscillation in the pressure chamber for ejecting ink drops from the corresponding nozzle; an ejection pulse number decision unit which decides the number of ejection pulses for the actuator in a current cycle based on a gradation value of print data for the actuator; a pulse addition determination unit which determines whether a control pulse that intensifies the pressure oscillation is to be added to the drive signal including the ejection pulses, based on a total of respective evaluation values set in an evaluation table in which, for each gradation value, an evaluation value 0 is set if the gradation value is equal to a reference gradation value, a positive evaluation value whose absolute value is increased as a gradation value is reduced is set if the gradation value is smaller than the reference gradation value, and a negative evaluation value whose absolute value is increased as a gradation value is increased is set if the gradation value is larger than the reference gradation value, the respective evaluation values being stored in the evaluation value table as being associated with the gradation values of the print data for the actuator and adjacent actuators for multiple recent cycles before the current cycle, wherein the pulse addition determination unit determines to not add the control pulse if the total evaluation value is a positive value, and determines to add the control pulse if the total evaluation value is a negative value; and a drive signal generation unit which generates the drive signal including ejection pulses whose number has been decided by the ejection pulse number decision unit when the pulse addition determination unit has determined to not add the control pulse, and generates the drive signal including the control pulse and ejection pulses whose number has been reduced from the number decided by the ejection pulse number decision unit when the pulse addition determination unit has determined to add the control pulse.