Piezo actuator and use of the same

The invention relates to a piezoelectric actuator (10), in particular for a fuel injector (100), with piezoelectric elements (55) stacked between an actuator foot (54) and an actuator head (53) in the direction of a longitudinal axis (61), which expand in the direction of the longitudinal axis (61) when an electrical voltage is applied, wherein the actuator head (53) is designed to actuate an element (52) connected at least indirectly to the actuator head (53), and with a tensioning device (65) having at least one prestressed tension spring (66), wherein the actuator foot (54) is in axial contact against a housing element (16) by the force generated by the at least one tension spring (66). According to the invention, it is provided that the at least one tension spring (66) at least partially radially surrounds the region between the actuator head (53) and the actuator foot (54), or is arranged laterally next to the region between the actuator head (53) and the actuator foot (54).