Abstract: Disclosed is a stacked piezoelectric actuator displaceable by bending comprising a plurality of piezoelectric ceramic layers stacked on one surface of a core material, and a plurality of piezoelectric ceramic layers stacked on the other surface thereof, said piezoelectric ceramic layers stacked on both surfaces being successively increased in piezoelectric constant d.sub.31 inner layers to outer layers. The piezoelectric coefficient d.sub.31 is derived from the following equation (2): ##EQU1## wherein k is the electromechanical coupling coefficient, the length vibration of a rectangular plate is taken as k.sub.31, and the unit of the piezoelectric coefficient d.sub.31 is C/N (m/V). The piezoelectric coefficient d.sub.33 in the longitudinal vibration of a column determined by the following equation (3) is a value for the whole stacked layers, and in the present invention, it is necessary that the piezoelectric coefficient d.sub.

Abstract: Disclosed is a knitting needle driving mechanism of a jacquard knitting machine for driving knitting needles by using piezo-electric elements in which a rear end portion of a piezo-electric body is movably supported in a groove of a supporting body or a housing, a front end portion of the piezo-electric body is movably connected to a rear end portion of a finger which is arranged so as to be aligned with the piezo-electric body and supported at the rear end portion thereof by the supporting body or the housing, and an intermediate portion between the front end portion and the rear end portion of the piezo-electric body is inserted into a rotatable member rotatably mounted on the supporting body or the housing. This knitting needle driving mechanism is small in size, high in response speed and prolonged in lifetime.