A Numerical Model for Piston Pin Lubrication in Internal Combustion Engines

As the piston pin works under significant mechanical load, it is susceptible to wear, seizure, and structural failure, especially in heavy duty internal combustion engines. It has been found that the friction loss associated with the pin is comparable to that of the piston, and can be reduced when the interface geometry is properly modified. However, the mechanism that leads to such friction reduction, as well as the approaches towards further improvement, remain unknown. This work develops a piston pin lubrication model capable of simulating the interaction between the pin, the piston, and the connecting rod. The model integrates dynamics, solid contact, oil transport, and lubrication theory, and applies an efficient numerical scheme with second order accuracy to solve the highly stiff equations. As a first approach, the current model assumes every component to be rigid. It is found that the pin interacts with the bottom of the connecting rod small end bearing and the top of the piston pin bore during almost the entire engine cycle, and the interfaces will be poorly lubricated unless there is relative rotation of the pin against both the other two components.