Integrated Design of Brushless DC Motors with Multi-Speed Hub Transmissions

• Main Authors: Bo-wei Lin, 林伯煒
• Other Authors: Yi-chang Wu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/67364781122793954146

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 99 === Brushless DC (BLDC) motors and multi-speed transmission hubs are key components for electric bicycles. Traditionally, BLDC motors and transmission hubs of electric bicycles are independently designed and manufactured. Then, they are combined appropriately to meet needed drive requirements. This kind of design strategy, however, suffers from inherent disadvantages on low efficiency, redundant mechanical elements usage, and incompact work space arrangements. The purpose of this study is to develop an innovative concept by integrating a BLDC motor with a transmission hub to form a compact structural assembly with desired functions for electric bicycles. First, a novel design concept is proposed by integrating an exterior rotor BLDC motor with a 3-speed transmission hub to form a compact structural assembly. Next, the equivalent magnetic circuit method is presented to determine the main dimensions of the BLDC motor, while the validity is verified by the finite element analysis (FEA). With the aid of fundamental circuits, the number of teeth of each gear for the transmission hub is then determined according to the desired velocity ratio of each speed. Finally, the detail design of the proposed integrated device is presented. Based on the results of FEA, the torque ripple is reduced form 20.79% to 16.87%, and the cogging torque is only 16% of the existing design. The efficiency of this integrated device can reach to 90%.