Patent ID: 7537300

Claim:
An inkjet printer comprising: an inkjet head having a piezoelectric actuator, a pressure chamber, and a nozzle; and a controller configured to apply a voltage to the piezoelectric actuator, wherein: the piezoelectric actuator forms a portion of a wall defining the pressure chamber; the piezoelectric actuator is configured to deform to project toward the pressure chamber and to change a volume of the pressure chamber while the controller applies the voltage to the piezoelectric actuator; the controller is configured to apply a first ink discharge signal and a second ink discharge signal to the piezoelectric actuator, each of the first ink discharge signal and the second ink discharge signal comprising: a first advanced voltage change from a first predetermined voltage to zero voltage to cause the volume of the pressure chamber to change from a first volume to a second volume which is greater than the first volume; and a first subsequent voltage change from zero voltage to the first predetermined voltage to cause the volume of the pressure chamber to change from the second volume to the first volume, the first subsequent voltage change being delayed for a predetermined period from the first advanced voltage change, wherein each of the first ink discharge signal and the second ink discharge signal causes an ink discharge operation from the nozzle; and the controller is further configured to apply an additional signal to the piezoelectric actuator between the first ink discharge signal and the second ink discharge signal, the additional signal comprising: a second advanced voltage change from the first predetermined voltage to a second predetermined voltage less than the first predetermined voltage to cause the volume of the pressure chamber to change from the first volume to a third volume which is greater than the first volume; and a second subsequent voltage change from the second predetermined voltage to the first predetermined voltage to cause the volume of the pressure chamber to change from the third volume to the first volume, wherein the additional signal does not cause the ink discharge operation from the nozzle.