Nobutaka Chiba

Mechanism of compression fatigue of wet friction materials

Abstract Wet friction materials are required to have long compression fatigue life, because they are used as wet clutches for transmitting and cutting off power repeatedly in automatic transmissions. In this study, it was found that the strength of wet friction materials decreased during compression fatigue testing because of the growth of their pore size. It was also observed that fatigue life differed depending on the fluid used, but that the deformation level at the time of failure was equal for various types of fluid.

The effect of surface texture on traction performance in a traction drive

In a traction drive, which transmits driving force by the shear strength of a traction fluid, surface texture is thought to be an important factor affecting traction performance. Therefore, the effect of surface texture on traction performance was studied using a two-roller tester. It was found that improving the surface texture increased the traction coefficient without increasing metal contact. Parameters such as the oil retention volume, V0, and the ratio between the reduced valley depths, Rvk, and core roughness depth, Rk, were also found to be important factors for increasing the traction coefficient without increasing metal contact.

Increase of Traction Coefficient by Means of Microtexture : 2nd Report, Optimization of Parameter in Microtexture and Application to Actual CVT(Machine Elements and Manufacturing)

The first report describes longitudinal surface texture was the best for improving the traction coefficient. Therefore, the longitudinal surface texture was optimized using the 4-roller tester. The test results made it clear that the groove depth, groove pitch and also the radius of curvature of the convex portion of the rolling elements are important parameters of the longitudinal grooves for improving the traction coefficient while assuring high durability at the same time. Furthermore, an attempt was made of increase traction coefficient of an actual CVT variator by using an optimized longitudinal surface texture. The test result proves that a traction coefficient can be improved by optimizing microtexture without spoiling durability.