Gearshift Quality Sensitivity Analysis

Gearshift quality is a perceived quality parameter. Hence, is getting much importance because of the increased awareness about comfortable and refined driving experience, especially in the case of passenger cars. When the topic of gearshift feeling is broached in manual transmission vehicles, synchronizer pack (shifter sleeve, engaging gear, strut, synchronizer and gear synchro ring assembly) have been the focus point for optimization. Synchronizer type (single, double or triple cone), lining material, datch chamfer angle of shifter sleeve/synchro ring of gear/synchronizer, all of these have been extensively studied in the past to improve the gearshift quality. With stringent timelines for vehicle development, OEMs prefer to use off-the-shelf powertrain systems developed by powertrain manufacturers. Due to this, avenues to refine gearshift feel gets reduced to a large extent and hence refinement becomes difficult. The scope of this paper is to discuss gearshift quality parameters used to assess the gearshift feel of a vehicle. It primarily examines ways to refine the gearshift quality by optimizing the external gearshift mechanism and other powertrain aggregates. It also extends to a sensitivity analysis of gearshift cables, gear shifter, dead weights and driveshaft on gearshift quality. Objective parameters were evaluated on vehicle level to understand the aspects of the gearshift, which when tweaked, resulted in an improved shift feel. Different proposals with regard to possible avenues were worked out for possible fine-tuning of the selected parameters. These were then validated on the vehicle. During the evaluation and optimization of gearshift quality, GSQA kit from M/s Ricardo was used to evaluate the gearshift quality.