란쥬반형 진동자를 이용한 초음파 회전모터에 관한 연구
(A) Study on the Ultrasonic Rotary Motor Using Langevin Type Vibrator
란쥬반형 진동자 초음파 회전모터;
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As industrial technology was developed, necessity for small size motor was increased on various fields such as medical treatment and robotics. The motor should be simple structure, and it has easy process of manufacture to overcome the limit of miniaturization. So, mode conversion type ultrasonic motor is enough to these conditions. In this paper, mode conversion type-single resonance mode ultrasonic rotary motor that use bolted Langevin type ultrasonic vibrator was studied. For the first time, this motor was proposed to Japanese Kumada in 1985. But In this study, finite element analysis of a stator, changed material of stator and rotor, bi-directional characteristics of rotor, miniaturization of the motor, and application possibility for card sending device was newly obtained. From result of finite element analysis, the aluminium was selected as metal material of Langevin type vibrator, because the fastest vibration velocity was received by aluminium material. And natural frequency (41.585 [kHz]) was confirmed in a longitudinal-bending-torsion vibration mode by modal analysis. Also, amplitude and phase of displacement according to frequency was confirmed by harmonic analysis. Elliptical trajectories of beam were made using results of harmonic analysis. And, the principle of bi-directional driving was proved by elliptical trajectories. HR-type motor, which has a heavy rotor and strong spring force, and LR-type motor, which has a light rotor and weak spring force were fabricated. In the case of LR-type, 38.0 [kHz] and 48.2 [kHz] were decided as driving frequency of clockwise and counterclockwise respectively. But in the case of HR-type, only clockwise driving was presented, and a driving frequency of 38.2 [kHz] was determined. Speed and torque of fabricated motor were changed in proportion to the electrical input voltages. The motor of HR-type, which has low speed and high torque, was estimated as a ideal model. And the speed of HR-type was linearly decreased according to increase of the load. Also, maximum efficiency of 6.28 [%] were obtained. A compact size motor, which has diameter of 10 [mm] and weigh of 9 [g], was fabricated to investigate possibility of miniaturization. And, 82.5 [kHz] and 91.6 [kHz] were decided as driving frequency of clockwise and counterclockwise respectively. But, Torque of the motor was not measured because of very low value. If this motor is applied to card sending device, it has fair advantage. First of all, Multiplex functions are performed by bearing-rotor, which use bearing directly. It has functions of bearing, friction material, rotor and roller. And, because of low speed and high torque characteristics many number of gear are reduced. Also, It is not different that size of the motor is reduced, because of simple structure and easy process of manufacture. So, This motor can have fair competitive power comparing with electromagnetic motor. However, vibrator supporting structure for stable driving of motor, durability of abrasion of coupler for long times use, low torque of compact size motor, low efficiency and some noise problems will have to improve by continuous study.