Piezoelectric transducer and an ultrasonic motor using the piezoelectric

Abstract

In the piezoelectric transducer, the elastic member vibrates, being excited by the first electromechanical transducing element. The impedance element on the second electromechanical transducing element is adjusted so that the vibration frequency and the resonance frequency of the elastic member should be almost the same. In the ultrasonic motor using the piezoelectric transducer, the vibration having the same frequency as that of the vibration of the elastic member is applied to the elastic member. This applied vibration has a direction differnt from that of the viration of the elastic member. The applied vibration and the vibration of the elastic member form approximate elliptical vibration, thereby rotating the rotor. The piezoelectric transducer of variable structure can control the resonance frequency in a wide range without electric power. The piezoelectric transducer can efficiently transduce applied electricity into approximate elliptical vibration of the elastic member, thereby generating great mechanical drive power. The electromechanical transducing element and the impedance element can compose a simple and compact vibration control unit. Since the electromechanical transcuding element and the impedance element form a closed circuit consuming no electric power, no power source circuit is required. The vibration control unit adjusts the resonance characteristic of the closed circuit, thus quantitatively controlling the frequency distribution and the amplitude of the mechanical vibration.