Patent ID: 6404108
Filing Date: 2002-06-11
Classification: F04D,H01H,H01L

Abstract:
A piezoelectric actuator, comprising:a piezoelectric element formed as a thin longitudinal plate having main opposing surfaces configured to undergo curving displacement in response to an applied driving signal; driver electrodes formed on opposing surfaces of said piezoelectric element, the driving signal being applied to said driver electrodes; a sensor electrode provided on one of the opposing surfaces for detecting displacement in said piezoelectric element, wherein one of said driver electrodes is in a predetermined configuration with respect to said sensor electrode; and an electrical feedback circuit connected to said sensor electrode and one of said driver electrodes for providing a feedback signal from said sensor to the one of said driver electrodes to eliminate electromechanical coupling which causes a primary vibration that is a result of a primary resonance frequency of the piezoelectric element; wherein said sensor electrode is disposed near the longitudinal center of the piezoelectric plate, and said predetermined configuration disposes said one of said driver electrodes such that it is axially symmetrical with respect to the longitudinal center of piezoelectric plate, and is predetermined so as to eliminate electromechanical coupling which causes secondary vibration during curving displacement of said piezoelectric element as a result of a secondary resonance frequency, the primary and secondary resonance frequencies being different from one another by setting the area distribution in the longitudinal direction in said secondary vibration mode so that the total charge of + charge and âˆ’ charge which occurs in said actuator is reduced to zero.