Patent ID: 8210831

Claim:
A piezoelectric pump comprising: a pump body including an opening; a diaphragm fixed to the pump body and arranged to close the opening, the diaphragm defining a pump chamber between the diaphragm and the pump body; and a piezoelectric element bonded only to a surface of the diaphragm opposite the pump chamber; wherein the diaphragm and the piezoelectric element are bonded to each other so as to define a diaphragm unit, the diaphragm unit being arranged to bend when a voltage is applied to the piezoelectric element; wherein the piezoelectric element comprises a stack of at least three piezoelectric material layers; wherein at least one of the at least three piezoelectric material layers is a neutral layer, the at least one neutral layer being stacked between piezoelectric material layers which expand and contract when a voltage is applied to the piezoelectric element; wherein the at least one neutral layer does not expand or contract when a voltage is applied to the piezoelectric element; and wherein when the diaphragm unit bends there is a neutral meeting point, at which compressive stress and tensile stress are zero, that extends through the at least one neutral layer along a curve thereof.