Non-metal Piezoelectric Motor Utilizing Langevin-Type Alumina/PZT Transducer Working in Orthogonal Bending Modes.

To apply ultrasonic motors (USMs) to the chemical industry, in this study, alumina is employed as vibrating bodies of transducers as it offers not only high chemical resistance but also a possibility to generate high output torques and power of motors due to the high Young’s modulus. First, a Langevin-type transducer was constructed by clamping several annular lead-zirconate-titanate (PZT) disks between two rod-shaped alumina vibrating bodies, and a traveling wave was excited to drive the rotor by a superposition of two orthogonal standing waves in bending modes. Subsequently, the performance of the alumina/PZT motor was assessed and compared to those of the metal/PZT motors with identical structures when the same voltage was applied. As predicted, the alumina/PZT motor provides higher performance than the metal/PZT ones. Since the alumina/PZT transducer has relatively high strain in its PZT disks owing to the high Young’s modulus of alumina, it exhibits a relatively high force factor, leading to a high output torque of the alumina/PZT motor. In the meantime, the transducer stores higher vibration energy due to the larger force factor; this enables the alumina/PZT motor to exhibit a higher output power. Besides, a higher rotation speed is obtained with this motor because the alumina/PZT transducer has a larger vibration velocity on the end surface. These results indicate the high applicability of alumina to high-power USMs as their vibrating bodies.