Miniature Ultrasonic Motor Using Shear Mode of Potassium Sodium Niobate-Based Lead-Free Piezoelectric Ceramics

Abstract

A miniature piezoelectric ultrasonic motor (USM) using the shear mode of (K,Na)NbO 3 (KNN)-based lead-free piezoelectric ceramics was developed. The motor can be driven in the shearing and bending vibration modes. By using the finite-element method, the motor vibration modes and driving mechanism were modeled. Both the ''soft-type'' (high-d USM) and ''hard-type'' (high-Q m USM) KNN-based lead-free piezoelectric ceramics were employed to clarify the characteristics of USMs. The experimental results reveal that the high-d USM widens the band of operational frequency in both vibration modes. In the shearing vibration mode, the high-d USM showed a revolution speed of 416 rpm, a torque of 41.5 mN m, and an efficiency of 0.6%, whereas the high-Q m USM showed the same characteristics of 313 rpm, 19.6 mN m and 1.6%, respectively. In the bending vibration mode, the characteristics of the high-Q m USM were 376 rpm, 51.4 mN m and 0.4%; however, the characters of the high-d USM deteriorated owing to the shift in resonance frequency caused by heat generation.

(K,Na)NbO3‐Based Lead‐Free Piezoceramics: Fundamental Aspects, Processing Technologies, and Remaining Challenges

“…The change in d 33 was comparable with that of PZT ceramics after 1000 cycles of thermal shock within the temperature ranging from −55°C to 125°C, which made a promising candidate for actuator applications . A miniature piezoelectric ultrasonic motor (USM; Tokyo Institute of Technology, Tokyo, Japan) was also fabricated using KNN ceramics, which can be driven in the shearing and bending vibration modes, also demonstrating good potential for actuator applications …”

Influence of the A/B Stoichiometry on Defect Structure, Sintering, and Microstructure in Undoped and Cu-Doped KNN

“…This may give rise to applications of this type of ceramics in specific fields [11]. Recent reports announced the fabrication of an ultrasonic shear mode motor prototype based on KNN-Li-Cu ceramic drive elements [45,46]. Moreover, Cu additions may play an important role when tailoring [3,23,42] or texturing [77] the microstructure of the KNN-based ceramics.…”

Next generation actuators leading breakthroughs

“…Since PZT contains lead that should be eliminated from all consumer goods, development of lead-free piezo elements with good property for actuators becomes a serious and urgent problem [8,9,10]. …”