A Design for Six Sigma Approach to Optimize a Front-Wheel-Drive Transmission for Improved Efficiency and Robustness 2011-01-0720

Environmental concerns and government regulations are factors that have led to an increased focus on fuel economy in the automotive industry. This paper identifies a method used to improve the efficiency of a front-wheel-drive (FWD) automatic transmission. In order to create improvements in large complex systems, it is key to have a large scope, to include as much of the system as possible. The approach taken in this work was to use Design for Six Sigma (DFSS) methodology. This was done to optimize as many of the front-wheel-drive transmission components as possible to increase robustness and efficiency. A focus of robustness, or consistency in torque transformation, is as important as the value of efficiency itself, because of the huge range of usage conditions. Therefore, it was necessary to find a solution of the best transmission component settings that would not depend on specific usage conditions such as temperatures, system pressures, or gear ratio. At the same time, this solution should not decrease the durability of the transmission. An optimization DFSS study was performed to learn how to maximize efficiency in the face of these usage conditions.

In the study, control factors such as lubrication flow modifications, clutch disks, separator plates, and the pump were explored. This paper shows how a solution was obtained that is more efficient, and less sensitive to usage conditions, including factors that induce wear. It also illustrates how a complex transmission can be optimized in hardware by focusing on torque transformation, after assessing 98,000 design iterations against a wide spectrum of usage conditions in just four weeks of testing.