Design and Optimization of an Innovative and Compact Gearbox Synchronizer

Synchronizers are mechanical devices used in gearboxes for braking the fastest shaft up to the angular velocity of the slowest one before engagement. Nowadays, many dual-clutch transmissions include an increasing number of gears in order to improve vehicle performance. However, they still use established and stable solutions for the synchronizers, counting a large number of parts to be manufactured with tight tolerances, and wide axial dimensions. So, the reduction of the synchronizer length is an important goal for the design of new gearboxes with a larger number of gears. The present research work studies a new solution for a shorter and simpler synchronizer. The main innovation is that the traditional conical clutch is replaced with a plane clutch including dog teeth, so that one part is performing both tasks of synchronization and engagement. The present paper discusses a first attempt dimensioning of the synchronizer in order to evaluate its feasibility. The layout was developed interactively with conceptual CAD models for representing the functionality of each element and with 3D printed prototypes in an electro-actuated test rig. This new synchronizer mechanism can be used in new dual-clutch transmissions, with electro-mechanical actuation and possibly with additional speed sensors.