Patent ID: 7857406

Claim:
An inkjet head driving apparatus which drives an inkjet head for use in gradation printing which is performed to cause a capacity of each of a plurality of pressure chambers filled with ink to be changed by a drive pulse applied to an actuator, an ink drop to be emitted onto a recording medium from a nozzle communicating with the corresponding pressure chamber, and the number of ink drops emitted to be controlled according to the number of drive pulses, the driving apparatus comprising: a drive signal generating section which, when the number of the ink drops is smaller than a predetermined number N (wherein 1<N≦M, and M is the number of ink drops at the maximum gradation), applies a deboost pulse to decrease pressure in the pressure chamber before the drive pulse for emitting a first drop of ink is applied and, when the number of the ink drops is equal to or greater than the predetermined number N, does not apply the deboost pulse, wherein the deboost pulse includes an expansion pulse applied to expand the capacity of the pressure chamber for a predetermined length of time or a contraction pulse applied to contract the capacity of the pressure chamber for a predetermined length of time, and a quiescent time following the expansion or contraction pulse.