Dynamic Behaviour of a Car Gearbox Under Gasoline Engine Excitations

The car gearbox is running under acyclism regime since it is excited by the variable load and speed generated by the Internal Combustion Engine (ICE). These excitations can be transmitted to the car driver through the gearbox. Most of the research works on its dynamic behavior considered a simple stage gearbox and four cylinders engine whereas the car gearbox is two stages of gears, and the three cylinders gasoline engine is frequently used. For this, the car gearbox was modelled to establish numerical motion equations using Lagrange method. Then, the load of the three cylinders gasoline engine is modelled as an external force. The gasoline engine speed at which the stiffness of the mesh is modelled with variable periods of time is a harmonic variable speed. Obtained results show that the external excitation of the ICE is more important than excitations due to contact conditions between gear teeth. Because of this, the acyclism frequency dominates the gear mesh frequency and we observe only the own frequency of acyclism in the spectrum of acceleration signal.