Bolt-Clamped Langevin-Type Transducer for Ultrasonic Motor used at Ultralow Temperature

Ultralow temperature environments are important for advanced scientific research areas, for example, chemical analysis technology. Some devices need to be operated in an ultralow temperature environment. However, actuators used in such an environment have low output power. As a result, some applications in an ultralow temperature environment have limited functions. This research aims to achieve a piezoelectric actuator having high output power at an ultralow temperature. A bolt-clamped Langevin-type transducer for an ultrasonic motor used in an ultralow temperature environment is proposed. The piezoelectric materials used in the transducer are affected by thermal stress when the temperature decreases from room temperature to an ultralow one. As a result, the materials break down or the performance of the transducer decreases. Thermal stress was simulated with the finite element method using some non-linear properties of materials in the transducer. The influence of the stress was evaluated by driving a transducer at an ultralow temperature obtained by using helium gas. An ultrasonic motor for use at an ultralow temperature was fabricated and evaluated. The maximum diameter and the height of the motor are 22 and 30.5 mm, respectively. The motor was successfully rotated at an ultralow temperature.