Patent ID: 6848763

Claim:
A drive unit for a liquid ejection head in which shrinkage of a pressure chamber and ejection of the liquid are caused by the application of a voltage to a piezoelectric body, comprising: means for applying a drive pulse with an electric field exceeding the coercive electric field of said piezoelectric body during the liquid ejection operation, the liquid ejection operation including a potential maintenance period, wherein an electric field value of said piezoelectric body in the potential maintenance period is about 10 times the coercive electric field; and means for applying a pulse that eliminates polarization remaining in said piezoelectric body to said piezoelectric body during no liquid ejection operation comprising a same-polarity voltage application period and an inverse-polarity voltage application period, wherein the pulse comprises a same-polarity pulse as the drive pulse and an inverse-polarity pulse with respect to the drive pulse, wherein an electric field value of said piezoelectric body in the same-polarity voltage application period is higher than the coercive electric field and an electric field value of said piezoelectric body in the inverse-polarity voltage application period is similar to the coercive electric field.