Patent ID: 7592738
Filing Date: 2009-09-22
Classification: H01L,H02N

Abstract:
1. An ultrasonic motor comprising: electromechanical transducers for driving; electromechanical transducers for vibration detection; and an ultrasonic vibrator in which, by supplying two-phase AC voltages with a predetermined phase difference and a predetermined driving frequency to the electromechanical transducers for driving, a longitudinal vibration mode and a flexural vibration mode are simultaneously generated to produce a substantially elliptical vibration at an output, wherein the ultrasonic motor includes a piezoelectric layered member which is made up of a stack of a rectangular-block-shaped piezoelectric ceramic sheets, wherein each of the piezoelectric ceramic sheets includes two columns of inner electrodes disposed in a longitudinal direction and three rows of the inner electrodes disposed in the width direction thereon, wherein an electromechanical transducer for driving is composed of two pairs of inner electrodes diagonally opposite to each other on the piezoelectric ceramic sheet, in which one pair of the inner electrodes is composed of A-phase electrodes and the other pair of the inner electrodes is composed of B-phase electrodes, wherein one inner electrode of a pair of the inner electrodes disposed along the longitudinal direction of the piezoelectric ceramic sheet at the central area in the width direction of the piezoelectric ceramic sheet is a C-phase electrode, and the other inner electrode is a D-phase electrode, wherein an electromechanical transducer for vibration detection is composed of the C-phase electrode and the D-phase electrode disposed at positions where the total of the electrical charges generated in each region due to the longitudinal vibration mode is finite and the difference between the charges generated in each region due to the longitudinal vibration mode is zero, and where the total of the electrical charges generated in each region due to the flexural vibration mode is zero and the difference between the charges generated in each region due to the flexural vibration mode is finite, and wherein the electromechanical transducers for vibration detection independently detect both the longitudinal vibration mode and the flexural vibration mode, wherein the longitudinal vibration mode and the flexural vibration mode are simultaneously generated by supplying two-phase alternating voltages to the electromagnetic transducer for driving.