PIEZOELECTRIC ACTUATOR, CLOCK, PORTABLE DEVICE AND METHOD OF DRIVING THE PIEZOELECTRIC ACTUATOR

摘要

PROBLEM TO BE SOLVED: To improve the driving efficiency without increase in size of an apparatus. SOLUTION: A vibration plate 10 of this piezoelectric actuator is provided with electrodes 33a, 33b, 33c formed on the surface of a piezoelectric element 30. The electrode 33a is provided for application of a voltage to excite longitudinal mode vibration in the vibration plate 10 by expanding and compressing the piezoelectric element 30. The electrodes 33b, 33c are provided to detect the vibrating condition of flexure vibration induced with the mechanical characteristic of the vibration plate 10 due to the excitation of the longitudinal vibration explained above. The drive frequency of voltage to be applied to the piezoelectric element is controlled to obtain large amplitude of the flexure vibration detected with the electrodes 33b, 33c.