On synchronization of heavy truck transmissions

Sammanfattning: Gear shifts are becoming more and more important as engines are adapted to low speed high torque working conditions. Synchronizers are key components for successful gear shifts. To adapt the synchronizers to new working conditions due to adaptations to new engines, improved development tools are needed. The presented thesis describes the development of two types of numerical models for the synchronization process, namely fluid-structure interaction to simulate the pre-synchronization phase and thermomechanical FE models to simulate the main synchronization phase. A methodology for developing friction models based on a combination of physical testing and numerical simulations is presented. Additionally, a comprehensive gear shift and synchronizer frame of reference section is presented.In paper A, two numerical fluid-structure interaction simulation models for assessing the pre-synchronization phase are presented. Simulations show that the synchronizer functionality is highly dependent on the gear shift maneuvering system, and that grooves in the synchronizer surface have a positive effect on the oil evacuation during the pre-synchronization phase.Paper B describes the development of a numerical thermomechanical model for simulating the main synchronization phase. Two parameter studies were performed, one based on external loads and one based on synchronizer geometry. The effect on the temperature increase from differences in thermal properties between molybdenum and carbon friction linings are presented.In paper C, a verification and validation methodology for highly transient thermomechanical processes was presented. Numerical verification, bulk temperature measurement, surface temperature measurement and qualitative visual inspection were combined to verify and validate the simulation model presented in paper B.In paper D, a methodology combining physical testing with an thermomechanical simulation model to develop a friction model was exemplified by a molybdenum coated synchronizer. A simplified thermal model was developed to remove the dependence of full finite element thermal models. The friction models shows good agreement with measured data.