A piston pin joint in a modern diesel engine operates under extreme loading and lubrication conditions. High load in combination with low relative surface velocities and limited lubrication makes this joint prone to localized wear and sudden failure. The analysis of this joint is also complicated with the pin motion, which defines surface velocities in the pin bore to pin and the pin to connecting rod interfaces. Therefore, the entire joint needs to be analyzed as a system of two bearings. Also, the hydrodynamic pressure in this joint at times may not be sufficient to balance the force applied to the joint and has to be complemented by the asperity contact pressure. The latter causes an additional deformation of the bearing. To address this problem a mixed lubrication model has been developed based on spectral EHD and nonlinear Greenwood and Trip statistical asperity contact formulation. Contact pressure distributions calculated with this model showed a pattern similar to the wear pattern in the bushing after production test. Analysis of the heat generated in the bearing was found to be a good indicator for the severity of the regime. Analysis of the bushing and piston bore with different geometry showed that asperity contact pressure and heat generated in the joint can be significantly reduced by modifications in local shape of the contacting surfaces.

High-powered Diesel engines typically use a timing gear train to couple/synchronize the camshaft rotation with the crankshaft and also to drive the accessories such as the fuel and oil pumps. In this paper a high-fidelity multibody dynamics model of a 6-cylinder inline Diesel engine and its timing gear train is presented. The multibody system representing the system is modeled using rigid bodies, torsional springs, revolute joints, prismatic joints, and rotational/linear actuators. A penalty model is used to impose joint and normal contact constraints. The normal contact penalty stiffness and damping techniques are used to model gear tooth stiffness and damping. The contact model detects contact between discrete points on the surface of a gear tooth (master contact surface) and a polygonal surface representation of the mating gear tooth (slave contact surface). A recursive bounding box/bounding sphere contact search algorithm is used to allow fast contact detection. Time-varying forces are applied to the cylinders to model the cylinder pressure variations due to combustion events as a function of the crank angle. The governing equations of motion are solved along with joint/constraint equations using a time-accurate explicit solution procedure. The model is partially validated by comparing its predictions of the torsional vibrations of a Diesel engine’s crankshaft and moving parts to experimental measurements. Emphasis is given on the practicality of the modeling methods to industry.

Environmental regulation and high fuel cost are among the leading driving forces behind the demand of energy efficient vehicles. Together with new engine hardware technologies, engine oil is expected to significantly contribute to improving vehicle fuel economy. New fuel-efficient engine oils are often formulated with advanced additives and low viscosity base oils. Understanding the lubrication performance at key engine components such as the cam and follower in valve train systems becomes critically important to ensure engine durability with the new fuel-efficient low viscosity oils. A full numerical mixed lubrication analysis of the cam and roller follower pair is conducted using the three dimensional line contact mixed elastohydrodynamic lubrication (EHL) model. The results show significant effects of surface roughness, topography, slide-to-roll ratio, and viscosity grade on lubricant film, contact pressure, and subsurface stress.

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