A Nut-type Ultrasonic Motor and Its Application on Focus System

摘要

This article reports a screw driving polyhedron linear ultrasonic motor (USM) of a nut type. It consists of a stator of a threaded metal nut bonded piezoelectric plates and a rotor with external thread. The piezoelectric plates are bonded to the fiat surface on the outside of the nut. A traveling wave in plane is stimulated on the stator when a harmonic electric signal is applied on the piezoelectric plates. The traveling wave drives the rotor to rotate and the threads transform the rotation into a linear motion. The lens could be fixed in the rotor and stator to obtain the auto focus and zoom and to realize the integrated design of focus system. This structure would omit retarder and directly drive to obtain a high accuracy of positioning and it is shockproof. The experiment data for a nut-type USM of M7 are obtained, when the applied voltages are 20-40 Vp-p and the working frequency 17 KHz for the second mode, the consumed power is 0.25 W, the moving speed is 0.5-1 mm/s in shaft direction, the driving force is about 5 g, and the response time less than 10 ms. A mini AF cellular phone module (8.5 × 8.5 × 5.9 mm~3) driven by this motor has been made. The image resolution of 3-5Mp has been obtained in the module prototypes of the cellular phone.