A MINIATURE HIGH-SPEED PIEZOELECTIRC MOTOR WITH A DISK-PIVOT STRUCTURE

Abstract

A miniature disk-pivot piezoelectric motor using a vibration mode B 11 of one nodal circle and one nodal diameter was investigated. Different from conventional wobble-type piezoelectric motor using piezoelectric rod or cylinder, a metal/piezoelectric disk is used to simulate the wobble vibration and an embedded metal cylinder is used to amplify the transverse displacement to obtain a much higher revolution speed over 10,000 rpm through the contact friction between the stator and rotor. The outer diameter of the metal/piezoelectric disk and the embedded cylinder is 14 mm and 2.5 mm, respectively. In order to avoid the coupling between the B 11 and any other vibration modes, the structure of the stator is analyzed using Finite Element Method (FEM) and optimized to avoid the influence between them. The simulations show that the stability of the disk-pivot piezoelectric motor will be influenced greatly when any other vibration mode is close to the mode B 11. To separate the coupling modes, two structure parameters can be modified: the thickness of the piezoelectric ceramic and the height of the middle metal cylinder on the stator. And these methods were proved through testing some prototypes of the motors.