Influence And Mechanism Of Surface Topography On Friction Characteristics Of Wet Clutches

Wet friction clutches are wildly used for automatic power-shift transmission of automobiles and construction vehicles. In particular, friction coefficient usually decreases with the increases of relative slipping speed between the paper friction plate and the steel separator plate. Such a friction characteristics occasionally gives rise to shudder or judder of vehicles. Research work reported in literature have shown that many factors, including the materials and surface textures of friction plate, the properties of automatic transmission fluid, operating conditions as well as aging state, affect the friction characteristics, and the relationships between the friction coefficient and these influencing factors are still not well understood.Many research have been finished to control the friction character, such as the develop of ATF and the paper-based friction material, but the influence of surface topography of separator plates on friction characteristics of wet clutches have not been studied.This thesis probes into the relation between the surface textures and the friction characteristics of the wet clutch, while the paper friction plate and the lubricant are stayed. During the study, the following works were finished and correlative results were got:(1) Based on statistical, signal processing and other mathematical techniques, the thesis selects 14 parameters which characterize 4 major aspects of a surface, i.e. the amplitude, function, space and combination properties, and then 5 most important parameters are selected based on Artificial Neural Networks.(2) Based on the shape of friction coefficient vs. sliding velocity curve under different test conditions, it is found that the film thickness is the main factors influencing on the friction characteristics. The thicker the oil film is, the more the friction coefficient decrease. Contrarily, when the oil film is very thin, the hydraulic friction increase much faster with the velocity increase, as a result, the dynamic friction coefficient increase.(3) By analysis on friction mechanism of wet clutches, it is believed that the following 5 factor, surface roughness, the oil storage ability, the oil viscidity, the shear strength of oil film, the ability to destroy oil film, affect the friction character mostly.(4) The Numerical Analyzing of the effect of surface textures on friction character is carried out, where the Reynolds Equation is employed to analysis the affect on friction character of texture shape, texture depth, texture area. The result indicates that the sphere aperture and the inclined groove textures can both improve the friction character.(5) At last, in order to validate the theory, 5 separator plates were treated by sandblasting, electrosparking, and laser treatment, and friction test are finished. The...