Design of End-Iron-Free Voice Coil Motor With Appropriate PM Length Ratio

Abstract

The linear voice coil motor (VCM) is widely used in many applications. Many research studies have been done to improve its thrust density. This article proposes a novel end-iron-free VCM topology to suppress the end effect on thrust loss. As the end iron yoke is removed, the reverse flux near the end of VCM has been greatly reduced. For a higher thrust density, the arrangement of unequal length between magnets is studied in terms of magnetic equivalent circuit (MEC) method. Through further electromagnetic analysis, the optimal permanent magnet (PM) length ratio is determined based on finite element analysis (FEA). The results from both FEA and practical experiments show that thrust characteristic and dynamic performance of the end-iron-free structure with appropriate PM length ratio is much better than those of the original structure, which proves the superiority of the proposed structure. Moreover, its cost and weight have been decreased. The proposed design plays a significant role in enhancing VCM performance and efficiency.