Manual transmission synchronization simulation of a heavy duty commercial vehicle and correlation with objective shift quality measurements

Gear synchronization performance defines the required force to be applied on gear knob, shifting time and gear knob travel. Heavy commercial vehicles (HCV) can be equipped with manual or automated transmissions. During the operation of both manual and automated transmissions, several shiftings are required as more than 8 up to 16 gears available on geartrain. Since, smooth and easy shifting are the critical asserts for the transmissions, technical investigations and developments on this field frequently performed. The analytical methods performed to analyze the performance of the shifting and synchronizer systems with different approaches. Moreover, objective measurement methods both applied to synchronizer itself and total shifting system including the numerical findings are available. In this study, manual transmission and gear synchronization performance have been investigated. The system selected for the study contains a 16 speed servo supported manual transmission and a gear shift cable mechanism. The synchronization process has a specific charachteristic that the physical contacts and regimes change step by step. During a gear synchronization, there are 8 main steps which are first free fly, start of angular velocity synchronization, angular velocity synchronization, turning the synchronizer ring, second free fly, start of the double bump, gear clutch turning and final free fly. Therefore, a model created to analyze the performance of the synchronization by seperating the equations and approaching all phases as a singular model. The performed numerical analyze contains the general physical properties of the system elements which enables modelling the physical system with axial and angular moment and force equilibrium equations. A MATLAB script has been performed to apply the mathematical equations prepared for all 8 synchronization phases. The ODE's (Ordinary Differential Equations) derived for the model has been solved with MATLAB using ODE solvers then. The input parameters are defined according to system properties and boundary conditions. As a verification for the model, main synchronizer parameters of cone angle, ring coating material and shifting system parameters of total mechanical ratio and cable efficiency have been modified to confirm the model success. The GSQA (Gear Shift Quality Assesment) method and test equipment is widely used in industry to evaluate shifting system and synchronizer performance from the transmission vehicle applications. Therefore GSQA tests have been performed for numerical analyze setup to provide objective data for the study. Afterwards, analytical model has been validated with the support of these objective test results that model enabled to be used as a prediction tool. At the end, different properties of the synchronizers and shifting system evaluated with the model analyzes to understood the effects of the changes of these parameters to the performance. The main parameters of cone angle, applied shift effort and ambient oil temperature have been analyzed with the simulation that the results are as expected. The increase of the ambient temperature decreases the shifting time with a minor effect and the decrease of the cone angle improves the shifting time and finally by increasing the shift effort applied to the gear knob the shift time again decreases according to the simulation based on the mathematical model.