Torque Converter Clutch Optimization: Improving Fuel Economy and Reducing Noise and Vibration

The torque converter and torque converter clutch are critical devices governing overall power transfer efficiency in automatic transmission powertrains. With calibrations becoming more aggressive to meet increasing fuel economy standards, the torque converter clutch is being applied over a wider range of driving conditions. At low engine speed and high engine torque, noise and vibration concerns originating from the driveline, powertrain or vehicle structure can supersede aggressive torque converter clutch scheduling. Understanding the torsional characteristics of the torque converter clutch and its interaction with the drivetrain can lead to a more robust design, operation in regions otherwise restricted by noise and vibration, and potential fuel economy improvement. The objective of this paper is to present a generalized integration summary for torque converter clutches (TCC) to enable aggressive apply at high engine torques and engine speeds below 1500 rpm without adversely affecting noise and vibration (N&V) performance. The focus is on optimizing existing damper technologies found in a large percentage of current production automatic transmissions. The overall goal is to demonstrate that through proper hardware selection and TCC calibration, a balance between N&V and fuel economy can be achieved. A validated lumped parameter modeling technique for optimizing torque converter clutch hardware that comprehends the complete powertrain and driveline system is used to investigate required TCC hardware. A torsional isolation metric across the powertrain is presented for comparing the performance of various damper designs. For operating points with inadequate isolation a controlled amount of slip across the torque converter clutch is required to increase isolation. An analytical methodology for minimizing the amount of slip required to satisfy noise and vibration targets and maximize fuel economy is reported. The effect of gear state, torque converter slip and power delivered to the driveline on fuel economy are also discussed based upon powertrain dynamometer measurements.