In four-wheel-drive vehicle, improving traction with the road surface enhances the vehicle's ability to respond to various driving conditions, increasing its overall versatility. Consequently, various studies have been conducted on four-wheel-drive vehicles that support torque distribution through electronic control. The driving unit that operates the transfer case assists in smooth torque distribution by providing high torque. Therefore, this study developed a reduction mechanism by vertically arranging a planetary gear set in the driving unit to increase the reduction ratio. To achieve this, a common ring gear with 52 teeth was used, and the design included a first-stage planetary gear with a sun gear having 18 teeth, a planet gear with 17 teeth, a second-stage sun gear with 12 teeth, and a planet gear with 20 teeth. The corresponding tooth profiles and structures were also designed. Based on this, a transfer case drive reduction module was developed, which improved torque performance: the first-stage planetary gear system provides 4.23 kgf·m of torque, and the second-stage planetary gear system achieves a final torque of 5.98 kgf·m

Abstract
1. 서 론
2. 구동부 감속 메 커니즘 설계
    2.1 감속 메 커니즘
    2.2 구동부 감속비 설정
3. 구동부 감속기 설계
    2.1 구동부 감속기 기어치형 설계
    2.1 유성기어 감속기 기어 설계
4. 결 론
References

• 염광욱(Division of Mechanical and Automotive Engineering, Han-Yang Cyber University) | Kwang-Wook Youm Corresponding author