Piezoelectric Oscillator and Ultrasonic Motor

A piezoelectric oscillator comprising:

• an oscillating body having a circumference and first and second surfaces;
• and
• (4/3)n piezoelectric elements secured to the first surface of the oscillating body and configured to generate an n-wave travelling wave that travels in a circular path by combining two B (1, n) mode standing waves that are out of phase with each other by 90° due to oscillation of the oscillating body, the (4/3)n piezoelectric elements being distributed in a circumferential direction of the travelling wave, and where n is a natural number,
• wherein, when a central angle around a center of the circumferential direction corresponding to a wavelength of the travelling wave is λθ, each piezoelectric element of the (4/3)n piezoelectric elements has a dimension corresponding to a central angle of λθ/2, and adjacent piezoelectric elements of the (4/3)n piezoelectric elements are spaced apart from each other at intervals each corresponding to a central angle of λθ/4 in the circumferential direction,
• wherein each piezoelectric element includes a piezoelectric body polarized in a thickness direction thereof and a pair of electrodes on respective opposite surfaces of the piezoelectric body, and
• wherein the (4/3)n piezoelectric elements are arranged such that alternating pairs of piezoelectric elements are polarized in opposite directions.