Mechanism of the Idle Gear Rattle Synchronized with Engine Rotation

The idle gear rattle of automobile manual transmissions in neutral position has been analyzed, and the mechanism of the excitation force synchronized with engine rotation has been clarified. Namely, the idle gear rattle occurs when the clutch disc spline backlash fluctuates by the off-center between the engine rotation and the transmission rotation, which results in a sudden change in the input shaft angular velocity. It is thus found that the larger become the off-center between the engine rotation and the transmission rotation, the maximum value of the clutch disc spline backlash, the angular velocity and angular acceleration of engine rotation, the greater becomes the excitation force of idle gear rattle.