Simulation to Estimate the Output Torque Characteristics and Temperature Rise of a Transmission Wet Clutch during the Engagement Process

During a typical shift event, one or more clutches are brought to engagement while others are released in order to change the torque transmission path. A mismatch in torque level and handshake timing between the off-going and on-coming clutches affects the shift quality. In order to capture the dynamic behavior of the torque response and estimate the temperature rise at the friction disk and separator plate interfaces during the engagement process, several numerical models have been developed. The earliest of these models was presented by Berger et al. which was later modified and enhanced by Natsumeda et al. and Yang et al. However, these models cannot capture the dynamic behavior of grooved clutch disks. Hence, development of a wet clutch engagement simulation model using commercial CFD simulation tool, which can capture the dynamic behaviors of no groove and grooved disks, becomes a pressing need. In this paper, we have presented an engagement simulation model using Star CCM+ simulation software and also discussed our observations from the simulation results. The key input parameters are squeeze velocity of the oil film, oil inlet temperature, initial rotating speed and flow rate. The porosity of the friction materials, friction co-efficient, compressive strain and flow factors are also taken into account. Our simulation model provides a helpful means to realize the influence of oil flow rate, rotating speed, applied pressure and groove patterns on the output torque behavior and temperature rise.