Development of Continuously Variable Transmission Fluid for Fuel Economy 2013-01-2584

We develop a new metal-belt continuously variable transmission fluid (CVTF) named FE to improve fuel economy and help reduce CO₂ emissions. FE is a low-viscosity fluid that reduces friction loss at low temperatures. Low-viscosity fluids generally reduce hardware durability, resulting in reduced metal fatigue life. Therefore, FE is designed for maintaining oil film thickness throughout the life of a vehicle by optimizing the base oil and viscosity modifier. FE also exhibits long-term anti-shudder performance that enables frequent use of controlled-slip torque converter clutches for improving fuel economy, represented by the flex start system, without decreasing torque capacity between the belt and pulley. The key point in the formulation of design is the selection of a suitable friction modifier. A friction modifier is an additive that improves friction properties. In this study, a suitable friction modifier selectively acts on friction papers as clutch material, not metals of belt and pulley surfaces, and provides a longer anti-shudder durability.

In this report, we present the concepts behind setting the performance targets and the formulation of the design of FE. Metal-to-metal friction, anti-shudder performance, and friction properties of shift clutches of FE are also evaluated and compared with other commercial CVTFs.