Piezoelectric ink jet print head including common laminar piezoelectric element for two or more ink jetting devices

Claim 1

A piezoelectric ink jet print head including a plurality of ink jetting devices each having an ink chamber whose volume is changed by a piezoelectric transducer to eject a droplet of ink, wherein the improvement comprises: a piezoelectric transducer consisting of a common laminar piezoelectric element disposed for activating a plurality of ink jetting devices, said common laminar piezoelectric element partially defining each said ink chamber of said plurality of ink jetting devices, said laminar piezoelectric element consisting of a plurality of piezoelectric ceramic layers and a plurality of electrode layers which are alternately laminated on each other; each of said plurality of piezoelectric ceramic layers being polarized in a polarizing direction perpendicular to a direction in which said piezoelectric ceramic layers and said electrode layers are laminated; voltage applying means for applying a voltage selectively to said plurality of electrode layers for displacing at least one of said plurality of piezoelectric ceramic layers in said polarizing direction, due to a piezoelectric shear effect, so as to change a volume of the ink chamber of a selected one of said plurality of ink jetting devices which corresponds to said at least one of the piezoelectric ceramic layers; and said electrode layers being formed of a thermistor which has a Curie point lower than that of said piezoelectric ceramic layers and which has a positive temperature coefficient of resistance so that said thermistor is an electrically insulating material at a temperature above the Curie point thereof.