Mahmud, S., Pahlovy, S., Kubota, M., Ogawa, M. et al., "Multi-Phase Simulation for Studying the Effect of Different Groove Profiles on the Drag Torque Characteristics of Transmission Wet Clutch," SAE Technical Paper 2016-01-1144, 2016, doi:10.4271/2016-01-1144.
Drag torque reduction is one of the key targets to improve the efficiency of transmission. Drag torque is generated by the automatic transmission fluid (ATF) that is circulated in the gap between the friction disks and separator plates for cooling purpose. Due to the relative motion between the friction disks and separator plates in disengaged mode, a shear stress is developed on the disks’ wall which gives rise to drag loss. The most conventional technique to suppress the drag loss is to cut grooves on the friction disk to facilitate smooth and faster discharge of the ATF. The shape of the grooves also plays a substantial role on the drag torque characteristics. Previously, we presented a simplified simulation model to predict the drag torque behavior of different grooves. However, the simplified model doesn’t include the oil inflow and outflow behavior from the oil inlet and outlet holes respectively. In this research, we presented an improved simulation model with an extended simulation domain to consider the effect of oil inflow and outflow behavior on the drag torque. This model helps us to realize the influence of the groove size and shape on the multi-phase drag torque behavior in more detail. The comparative profile of different grooves obtained from simulation reflects close similarity with the test result. Therefore, the simulation model leads to a convenient method of optimizing the size and shape of the grooves and plays a pivotal role to select better groove pattern for the suppression of drag loss.