Minimizing Tooth Mesh Misalignment in Heavy Duty Tractor Transmission 2016-01-8069

In any drive system, tooth mesh misalignment originates primarily from its torque transmitting components such as spline connections, gears, shafts, bearings and housing. The major influencing factors for tooth mesh misalignments are clearance between components, deflection, stiffness, thermal expansion, manufacturing limitations and assembly limitations. Tooth mesh misalignments in heavy duty off-highway applications like tractor, propagates drastically while handling severe loads and tends to shift the load distribution in a gear pair to an un-biased manner along the facewidth, resulting in high contact stresses and poor transmission performance. Misalignments definitely add few more decibels to the driveline system which will be an annoyance to the user. Moreover, mesh misalignments in any drive system cannot be eliminated and hence different approaches and methods were followed to compensate the misalignment.

Current tractor drivelines are geared up to accommodate new technologies and updates experienced throughout the industry. One such phenomenon is the use of wet clutch in forward and reverse tractor application. The applications include agriculture, livestock, construction, material handling, etc. In all such heavy duty tractor applications in particular, gears that are connected with the wet clutch assembly experiences severe cyclic loading and duty cycle. Misalignments in this case, will directly affect the performance of drive system to a substantial amount.

This paper revolves on the case study of two factors influencing mesh misalignment: (1) bearing offset and (2) gear hub, as an initiative to minimize the amount of tooth mesh misalignment on gear pair. Advanced driveline analysis tools like KISSsoft and MASTA were used to analyze and calculate the amount of misalignment on the gear tooth mesh. The optimized gear pair showed more than 40% reduction in tooth mesh misalignment and more than 10% reduction in peak contact stress during initial design stage.