Multilayer piezoelectric linear ultrasonic motor for camera module

Piezoelectric linear ultrasonic motors have been widely studied for auto focusing devices of digital cameras and cellular phones due to their simple structure. A piezoelectric motor operated at low voltages, not achievable using bulk piezoelectrics, is required for the camera module of cellular phone. In this study, a tiny piezoelectric linear motor was fabricated and its dynamic properties at low voltages were analyzed. To reduce the driving voltage, thin multilayer ceramics fabricated by a tape casting method were applied to the motor. The proper number of layers of the piezoelectric element was determined by ATILA simulation program. As a result of the simulation, the largest displacement of the shaft was observed at 21 layers. Characteristics of the motor were analyzed with respect to applied voltages and frictional forces between the mobile element and shaft. Velocity and force of the motor increased with increasing applied voltage. The motor exhibited a velocity of 10.9 mm/s and a thrust force of 110 mN at a frictional force of 62.5 mN and an applied voltage of 10 Vp-p.