Analysis of the performance of piston pin bearing in mixed lubrication

Based on the EHL theory, the average flow model and the asperity contact theory, the study is presented for mixed lubrication of piston pin bearing. Firstly, the piston pin boss bearing, the piston pin and the connecting rod small end bearings were taken as a whole system, and the fourth-order Runge-Kutta method was used to solve the rotation speed of the piston pin operating in hydrodynamic lubrication. Good agreement is obtained among the results when the spectral technique was used. Secondly, the oil film pressure distribution and the asperity contact pressure distribution were numerically solved when elastic deformation was taken into consideration, and the effect of engine speed on the minimum film thickness ratio and friction distribution was analyzed. The results showed that piston pin bearing was operating under mixed lubrication condition from the latter period of the compression stroke to the first period of the exhaust stroke of engine cycle. Friction of piston pin bearing decreases during the process while the engine speed is up to a critical value, and friction increases obviously when engine speed is over the critical value. Once elastic deformation is taken into the consideration, the contacting pressure distribution will be changed in axial direction, with the pattern of small pressure value in the middle and large value at the ends. This shows the same failure behavior of piston pin bearing.