Patent ID: 7802864

Claim:
A driving method of an inkjet head including a plurality of nozzles that eject one or more ink droplets to print a dot of a tone corresponding to the number of ink droplets, a plurality of pressure chambers that are communicated with said nozzles respectively, adjacent to each other, and separated by partitions, and a common pressure chamber that supplies ink to said pressure chambers, comprising: providing a plurality of actuators for said pressure chambers that change volumes of said pressure chambers according to drive voltages; and applying a series of drive pulse signals for the number of ink droplets to be ejected as the drive voltage to each of said actuators in each cycle time Tc which is a print cycle of one dot, wherein the cycle time Tc, the number of ink droplets N for a maximum tone, output time Td k (where k=1, 2, 3, . . . N) in which the drive pulse signal is applied for ejection of each ink droplet, and an inactive period Te in which said pressure chambers are made inactive from an end of application of a final drive pulse signal for the maximum tone to a start of the next cycle time Tc are set in a relationship of Tc=(Td 1 +Td 2 +Td 3 + . . . +Td N )+Te, the inactive period Te is set, by referencing pressure propagation time Ta of a pressure wave that propagates in each of said pressure chambers from said common pressure chamber to said nozzle, in a relationship of Te=(0.5+m)×Ta (where m (natural number)=1, 2, 3, . . . ), time Tr k (where k=1, 2, 3 . . . N) from a start of the next cycle time Tc to application of an initial drive pulse signal for a tone other than the maximum tone is set in a relationship of Tr k =n×Ta (where n (natural number)=1, 2, 3, . . . ), and further, a relationship of Tr 1 >Tr 2 >Tr 3 . . . >Tr N-1 is established.