Performance Characterization of Automatic Transmission Upshifts with Reduced Shift Times 2015-01-1086
As the number of fixed gear ratios in automatic transmissions continues to increase in the pursuit of powertrain system efficiency, particular consideration must continue to be focused on optimizing the design for shifting performance. This investigation focuses on the effect of shift time on the performance attributes of shift quality, durability, on schedule fuel consumption and enablers to further reduce shift time. A review of fundamental design features that enable reduced shift times in both planetary and dual clutch transmissions is presented along with key operating features of both the transmission and engine/prime mover. A lumped parameter metric is proposed to assess and compare the upshift controllability of new transmission architectures and powerflows using simple analysis. The durability of fast shift times during performance maneuvers are quantified through calculation of shifting clutch energy and power from analysis and form measurements on a powertrain dynamometer. In addition to perceived powertrain performance, powertrain dynamometer measurements running the FTP test schedules fuel consumption trends with respect to inertia phase shift time and can provide upwards of 1.25% by optimization of shift times depending on powertrain details. The paper concludes with vehicle measurements comparing part and wide-open throttle shift times for 6 and 8 speed planetary automatics transmissions.