Tailor-made multilayer piezoelectric actuator having large displacements and forces produced from lead-free piezoelectric ceramics

We propose tailor-made multilayer piezoelectric actuators (TAMPA) having large displacements and large forces. In existing piezoelectric actuators, production of small, low-cost actuators having large displacements and large forces is difficult to achieve. We solved this problem by combining two bimorph-type piezoelectric elements with both ends simply supported, and stacking several elements on top of each other. Moreover, TAMPA is a tailor-made actuator whose displacement to force ratio can be varied widely by adjusting the size of the bimorph-type piezoelectric elements even when the total size of the actuator is kept constant. In this study, the bimorph-type piezoelectric element was analyzed, and the relationship between the displacement and the force under fixed conditions was experimentally determined. The relationship between the displacement and the force of TAMPA was theoretically derived. The analytical results showed that a TAMPA having dimensions of approximately 10times10times10 mm is capable of generating displacements of several hundred mum or the force of several N. A prototype was produced and its performance was evaluated. These results agreed well with the analytical results, confirming the validity of the analytical results. Finally, because the lead in PZT can cause environmental problems, a TAMPA was produced that used (K,Na)(Nb,Ta)O₃ piezoelectric ceramics instead of PZT