Piezoelectric Torsional Vibration Driven Motor
Patent application, filed 29 Oct 2000,
DEPARTMENT OF THE NAVY WASHINGTON DC
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A high power and high torque density piezoelectric motor is developed using torsional actuator tube stator directly coupled to the rotor via one or two one way clutches. A cylindrical torsional actuator is comprised of a plurality of tubular piezoelectric ceramic segments poled along their length, aligned in alternate polarity and bonded together with intervening electrodes. When an alternating electric field is applied to the electrodes across adjacent segments to actuate the segments in their shear resonance mode, an end of the cylindrical actuator moves in a direction perpendicular to the length of the cylindrical actuator in response to the applied electric field. In a half cycle torsional motor, the angular motion of the end of the cylindrical actuator is transmitted to a rotor via a one way roller clutch positioned at one end of the cylindrical actuator. A full cycle motor has a second one way clutch positioned at the other end of the cylindrical actuator tube such that both ends of the tube vibrate in opposite angular directions. These rotary displacements contributed alternatively from both ends of the cylindrical actuator stator are selectively transmitted to the rotor in unidirectional rotary motion via a set of one-way clutches. The clutches are built into both ends of the stator tube in such an orientation that the minute strokes are accumulated by converting the high frequency mechanical vibrations into continuous or step-wise motion of the rotor. Thus the power generated in the piezoelectric element is converted directly into rotary motion of the rotor, and thus this coupling mechanism results in a highly efficient motor. Specific values of the torsional angle and torque can be tailored for each application, by varying the actuator material, geometry and the applied alternating electric field.
- Electrical and Electronic Equipment
- Electricity and Magnetism