Patent ID: 7157837

Claim:
A piezoelectric actuator, comprising: a plurality of piezoelectric layers each of which is formed of a piezoelectric material, wherein the plurality of piezoelectric layers include at least one first piezoelectric layer, and at least one second piezoelectric layer; a plurality of electrode layers which are stacked alternately with the piezoelectric layers, wherein the plurality of electrode layers comprise at least three electrode layers including a first pair of electrode layers which cooperate with each other to sandwich said at least one first piezoelectric layer, and a second pair of electrode layers which cooperate with each other to sandwich said at least one second piezoelectric layer; and at least one active portion which is provided by respective portions of said at least one first piezoelectric layer and said at least one second piezoelectric layer, such that each of said respective portions is sandwiched by a corresponding pair of electrode layers of the first pair of electrode layers and the second pair of electrode layers, said corresponding pair of electrode layers being opposed to each other in a direction of the alternate stacking of the piezoelectric layers and the electrode layers, said at least one active portion being deformed when an electric voltage is applied to the plurality of electrode layers, wherein said at least one first piezoelectric layer has a first thickness equal to a distance between the two electrodes of the first pair, and said at least one second piezoelectric layer has a second thickness which is equal to a distance between the two electrodes of the second pair and is greater than the first thickness.