For the purpose of enhancing the fuel economy in compact cars, it has been tried to extend the lock-up rpm of damper clutch in automatic transmission. But this way is likely to cause the interior booming noise accompanied by the body vibration. This is why lowering the engine rpm, where the damper clutch starts to be locked up, makes the powertrain vibration increase due to the shortage of the engine power compared to the vehicle load.
Therefore, this study will examine the causes and paths of the booming noise and body vibration caused by extending the damper clutch lock-up rpm to lower region. In other words, when the damper clutch runs in locked-up state, this study will examine the increment of the powertrain vibration, the transfer paths of the powertrain vibration and the resonating body system.
Specially, this study will use RMA (Running Mode Analysis) method. Through investigation, this study will propose a few kinds of structural modifications and among these modifications the optimized modification will be adopted as the refinement of the booming noise and the body vibration.