A piezoelectric motor comprising:
- a rotor;
- a stator in the form of hollow cylindrical waveguide formed of a piezoelectric material which is homogeneously polarized uniformly in a polarization direction which is in a radial direction of said hollow cylindrical waveguide, said hollow cylindrical waveguide having a first end surface, a second end surface, an external cylindrical surface and an internal cylindrical surface;
- said rotor being in contact with said first end surface of said hollow cylindrical waveguide;
- generators for generating an longitudinal traveling wave, in the form of an expansion-compression traveling wave having a wave length .lambda. and traveling circumferentially on said first end surface, said longitudinal traveling wave being generated from expansion-compression standing waves on said first end surface generated said generators;
- each of said generators including:
- a first generator for producing a first expansion-compression standing wave of said expansion-compression standing waves, said first generator including first and second electrodes respectively on said external cylindrical surface and said internal cylindrical surface which extend perpendicularly to said polarization direction and oppose one another and are disposed on a first sector of said hollow cylindrical waveguide having a circumferential length of .lambda./3;
- a second generator for producing a second expansion-compression standing wave of said expansion-compression standing waves, said second generator including first and second electrodes respectively on said external cylindrical surface and said internal cylindrical surface which extend perpendicularly to said polarization direction and oppose one another and are disposed on a second sector of said hollow cylindrical waveguide having a circumferential length of .lambda./3;
- a third generator for producing a third expansion-compression standing wave of said expansion-compression standing waves, said third generator including first and second electrodes respectively on said external cylindrical surface and said internal cylindrical surface which extend perpendicularly to said polarization direction and oppose one another and are disposed on a third sector of said hollow cylindrical waveguide having a circumferential length of .lambda./3;
- said first, second and third sectors being disposed adjacent one another and together forming a generator sector having a circumferential length of .lambda.;
- and
- energizing means for driving said first and second electrodes of said first, second and third generators such that said first, second and third expansion-compression standing waves are phase shift from each other by 2 .pi./3 to produce said expansion-compression traveling wave having said wave length .lambda. to rotate said rotor by means of frictional contact between said first end surface and said rotor;
- and
- said hollow cylindrical waveguide having a circumferential length equal to N number of said wave length .lambda. of said expansion-compression traveling wave wherein N is an integer equal to at least one, and said generators including N number of said generators with said generator sectors thereof disposed adjacent one another.