The general auto transmission uses the torque converter that has a good vibration damping force by launching performance and damping effect as power transfer unit. The vehicle equipped with auto transmission uses Lock up clutch system to improve the fuel efficiency. The Lock up clutch system is the major factor of the devices that increase the torque from engine to transmission in specific condition and also consist of the damper springs to transfer the torque stably. Damper spring controls the vibration of power transfer units and improve the impression of riding and durability, by being damping function on change torque from engine. In addition, not only the appearance and performance, but also these sensitive qualities as like vibration and noise can also be main factor to buy a car. Recently, in order to absorb the low vibration caused by vehicle structure vibration, the Low-stiffness damper has been on the rise. The damper spring should be considered and designed, considering the engine characteristic and direct connect of lock up clutch due to the stiffness of the spring and hysteresis has a major effects to the damper characteristic. This study can be used for analyzing the major factors to effect the NVH characteristic by evaluating the damper’s hysteresis according to change of spring stiffness.

1. 서 론
 2. 댐퍼 시스템 구조 및 작동 메커니즘
 3. 시험 방법 및 조건
  3.1 시험방법
  3.2 시험장치 및 조건
 4. 시험 결과 및 고찰
 4. 결 론
 References

• 윤영길(한국파워트레인(주)) | Young-Kil Yoon
• 문윤배(수성대학교 컴퓨터기계설계과) | Yun-Bae Moon Corresponding Author