Structural Analysis of Belleville Spring Used in Automatic Shift Transmission Multi-Plate Wet Clutch for Off-Highway Application

In the present article, structural spring characteristics of two different Belleville springs are analyzed to overcome a failure issue in an automatic shift transmission clutch system. The spring design is evaluated through explicit dynamics analysis by finite element modelling and validated by DIN 2093 standard. Automatic shift transmissions that are used in off-highway vehicles are employed with multi-plate wet clutch system to actuate the planetary gears. These clutches are actuated through automatic transmission fluid that are supplied through flow channels. The clutch piston is moved axially by fluid pressure against the clutch pack and Belleville spring thereby transfers torque. Meanwhile, the clutch piston is retracted by the spring force once the fluid pressure is cut off. The spring is designed in such a way that during the energizing mechanism, positive spring stiffness is maintained. It is noticed that the clutch function is obstructed as the spring is inverted to other side due to unstable negative stiffness characteristic. It stalls the function of clutch system and automatic shift transmission thereby vehicle becomes inoperable. The present study compares two different spring characteristics required to suit the clutch design for proper function of transmission system.