Ultrasonic motors—breakthrough trials for the next generation

Abstract

Twenty years and more have passed since real research of ultrasonic motors was started and now their practical applications are performed in some engineering fields. Therefore, such a problem has happened now as to what kinds of breakthrough ultrasonic motors must be researched for the next generation. For this reason, we are challenging the breakthrough research of the ultrasonic motors. This paper deals with such breakthrough motors. In the first part, we deal with thin-form ultrasonic motors of high revolution speed for their use as HDD motors, applying lead-free piezoelectric single crystal of LiNbO3. The second part contains some gyro-moment motors, devised by us originally. The motors can be driven electromagnetically and, moreover, electrostatically in theory. Therefore the motors are suited to ones fabricated by MEMS technology and might be applied as a micro-fun motor for heat radiation in electronic apparatuses, a windmill motor in fuel cells, and so on.

Design and Characteristics of Mode-Coupling LiNbO3 Ultrasonic Motor Depended on Width-to-Length Ratio of the Stator Vibrator

“…[5][6][7][8] Similarly, a piezoelectric single crystal has been investigated for applications in SAW linear-type motors, 9,10) and we reported bulk-mode resonant-type USMs fabricated using a LiNbO 3 plate. 11,12) Although the piezoelectric constants of LiNbO 3 are smaller than those of leadcontained piezoceramics, a LiNbO 3 resonator has a small dielectric loss and a small deterioration of vibrational characteristics even when the vibration velocity is large. 13,14) These features indicate that a single-crystal resonator is suitable for miniature motors driven at a relatively high frequency.…”

Single Phase Drive Ultrasonic Motor Using LiNbO3 Rectangular Vibrator

“…Consequently, the authors are working toward a new high-speed rotational ultrasonic motor with a thin shaft rotor, 9) and we have studied some LiNbO 3 biphase motors, the main feature of which is reduced thickness and high revolution speed exceeding 5000 rpm. 10,11) Moreover, a single phase drive motor has been presented for which a simple drive and structure without electrode division for greater miniaturization. The single phase motor is composed of a diagonally symmetric vibrator with a mode coupling phenomenon.…”

Measurement of LiNbO3 Rectangular Plate Under Large Vibration Velocity of the First Longitudinal and Second Flexural Modes

“…8,9) The authors have studied some LiNbO 3 ultrasonic motors, the feature of which includes thinness and high revolution speeds exceeding 5000 rpm. [10][11][12] The LiNbO 3 stator vibrator, for example, is used in a resonance mode and is characterized by a low heat generation and high vibration level; however, the vibrator fractures itself without any warning when the vibrational velocity exceeds the fracture limit. Therefore, we must obtain the particulars of vibrator characteristics at a high vibrational level and at the fracture limit.…”