Toshikazu Nanbu

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.

Surface Finishing on Arc-Shaped Inner Surface by Ultraviolet Assisted Polishing

Recently, diamonds have been utilized gradually for sliding parts and wear-resistant parts because of their excellent properties. The shape of diamond applied to these parts is not only plane but also arc-shaped inner surface. Therefore, development of diamond polishing technology is required. In this study, ultraviolet assisted polishing was thought to develop to polish polycrystalline diamond (PCD) on arc-shaped inner surface. The authors investigated effect of ultraviolet radiation on polishing efficiency and surface roughness. As a result, the surface roughness Ra of PCD showed less than 15 nanometers. In addition, polishing efficiency was improved about 30 percent due to ultraviolet assisted polishing.

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.

Increase of Traction Coefficient due to Microtexture (1st Repor, Effect of Orientation in Microtexture)

Improving the traction coefficient of a traction drive system is a key factor in obtaining a smaller, lighter unit and also greater torque capacity. This study focused on the microtexture of the rolling elements, and effect of orientation in microtexture was examined with the aim of improving the traction coefficient in the viscous region. Three textures-dimple, transverse and longitudinal-were examined using a 4-roller tester that enabled tests to be conducted under high pressure and high rolling speed. As a result, it was found that the longitudinal surface texture is the best for improving the traction coefficient. The results obtained with EHL analysis showed that only the surface texture with longitudinal grooves improved the traction coefficient, just as in the tests conducted with the 4-roller tester.