Patent ID: 7608982

Claim:
A stacked type piezoelectric element, comprising: a plurality of piezoelectric layers stacked one on another; and electrodes that are each arranged between the piezoelectric layers and divided into a plurality of inner electrodes, the electrodes including: 1) a first group of driving electrodes, to each of which a first predetermined AC voltage is applied so as to drive the stacked type piezoelectric element, 2) a second group of driving electrodes, to each of which a second predetermined AC voltage having a phase different from that of the first predetermined AC voltage by π/2 (rad) is applied so as to drive the stacked type piezoelectric element, and 3) a sensor electrode, to which neither the first nor second predetermined AC voltage is applied and which generates an output signal, wherein at least a part of the driving electrodes is exposed to an outside thereof and the area of at least one of the driving electrodes in the first group is greater than that of any one of the driving electrodes in the second group so as to reduce the difference between the cumulative area of the driving electrodes in the first group and the cumulative area of the driving electrodes in the second group, the difference resulting from the existence of the sensor electrode.