Patent ID: 8519599

Claim:
A piezoelectric actuator unit comprising: a piezoelectric layer; a first electrode and a second electrode which are arranged to sandwich the piezoelectric layer therebetween to form a substantive capacitor element in which an active portion of the piezoelectric layer sandwiched between the first and second electrodes is defined, the first electrode includes a plurality of individual electrodes, and the second electrode includes a first common electrode and a second common electrode both of which are provided in common to the individual electrodes, and the active portion includes a plurality of first active portions each of which is sandwiched between one of the individual electrodes and the first common electrode, and a plurality of second active portions each of which is sandwiched between one of the individual electrodes and the second common electrode, the substantive capacitor element includes: a plurality of first substantive capacitor elements each of which has one of the individual electrodes, the first common electrode and one of the first active portions sandwiched between the one of the individual electrodes and the first common electrode; and a plurality of second substantive capacitor elements each of which has one of the individual electrodes, the second common electrode and one of the second active portions sandwiched between the one of the individual electrodes and the second common electrode; a capacitor which is connected in series to the substantive capacitor element; and a voltage applying mechanism which applies a first voltage to the capacitor, and applies a second voltage between the first electrode and the second electrode of the substantive capacitor element to cause a piezoelectric deformation in the active portion of the piezoelectric layer, the capacitor includes a first capacitor which is arranged between the first common electrode and the voltage applying mechanism, and a second capacitor which is arranged between the second common electrode and the voltage applying mechanism, the voltage applying mechanism applies a first electric potential to the first common electrode via the first capacitor at all time, applies a second electric potential which is different from the first electric potential to the second common electrode via the second capacitor at all time, and switches an electric potential of each of the individual electrodes between the first electric potential and the second electric potential, and the first capacitor is connected to the plurality of first substantive capacitor elements commonly, and the second capacitor is connected to the plurality of second substantive capacitor elements commonly.