Gearset Synchronization Modeling of a Heavy Commercial Vehicle Transmission and Correlation with Objective Measurements of Gear Shift Quality

For manual transmissions, including the automated types, reduced shifting effort and easy of gear set engagements in a short period of time without rattles and shakes are major requirements for the shift quality evaluations. Performance of the synchronizer mechanisms depends highly on the design, material and arrangement of the transmission synchronization components; thus, the synchronization process is a mechanical and tribological process which is influenced by numerous design parameters of the synchronizers, constraints and properties of the lubricated contacts. In this study, a detailed multi-body-dynamics model for a HCV (Heavy Commercial Vehicle) transmission gearset is presented; various synchronization simulations are performed and the results are compared with the objective shift quality measurements. The developed model yields total synchronization and engagement time based on the applied gear shifting effort. The translational and rotational movements are calculated using the force and moment balance in each stage of the synchronization process solving the governing differential equations numerically. Synchronizer mechanisms are frictional lock-up mechanisms that the synchronization process needs to be considered and evaluated step by step due to the transient nature of lubrication regimes from hydrodynamic to boundary as a result of changing lubricant film thickness, oil viscosity and kinetic coefficient of friction. Besides, the transmission shifting system has complex linkages and detents that is included in the model because of their significant influence on the shift quality. The developed gear set synchronization model was validated using objective GSQA (Gear Shift Quality) measurements obtained in real heavy duty commercial vehicle field tests and various shifting scenarios were simulated. The effects of principal synchronizer design parameters and level of applied force on the shift quality characteristics were discussed in detail.