Patent ID: 8063538

Claim:
An ultrasonic motor comprising: a stator; and a rotor, wherein the stator includes a vibrating member having a circular or polygonal outer circumferential edge; and 4n piezoelectric elements secured to a first surface of the vibrating member and configured to generate a 3n wave that travels in a circulating manner when the vibrating member vibrates, the 4n piezoelectric elements being disposed in a circumferential direction of the vibrating member along a direction in which the 3n wave circulates, wherein n is a natural number, wherein a center angle around a center of the vibrating member in the circumferential direction and corresponding to a wavelength of the 3n wave is λ θ , each piezoelectric element has a size corresponding to λ θ /2 of the center angle, and adjacent piezoelectric elements of the 4n piezoelectric elements are separated from each other by an interval corresponding to λ θ /4 the center angle along the circumferential direction, wherein each 4n piezoelectric element includes a piezoelectric member and a pair of electrodes on opposed respective surfaces of the piezoelectric member, wherein the piezoelectric member of each 4n piezoelectric element is polarized in a same thickness direction as the piezoelectric member of the 4n piezoelectric element adjacent thereto at a first side thereof in the circumferential direction, wherein the piezoelectric member of each 4n piezoelectric element is polarized in an opposite thickness direction to the piezoelectric member of the 4n piezoelectric element adjacent thereto at a second side thereof in the circumferential direction, and wherein the rotor is disposed so as to be in contact with the stator, the rotor configured to rotate by receiving vibration resulting from the 3n-wave generated by the stator.