Timing Chain Wear Assessment with Different Type of Oils 2009-01-0198
One of the commonly used torque transfer elements used on internal combustion engines is the chain, due to its high strength to wear ratio. Chain is an assembly of a number of sub-components that consists of pins, bushes, rollers and plates. There are two primary failure modes with a base engine chain drive system. The first is a progressive failure which results from an apparent elongation of the chain due to wear. Elongation of the chain results with engine timing deviation and performance loss at early stages. In particular cases, when design limit for chain elongation is exceeded, the chain begins to skip over sprocket teeth. The second, which is a hard failure, is a catastrophic failure of the chain due to tensile fatigue loading of the weakest components of the chain (mainly bush or plate) .
In this study, accelerated dynamometer durability with a unique test cycle to simulate the engine running lifetime has been used to distinguish the performances of different types of lubricant (a mineral, semi-synthetic and fully-synthetic) on a standard type endless bushing chain. Chains have been regularly measured during tests in order to build up the wear elongation trend. They have also been applied to teardown inspections at the end of tests that are supported with SEM investigations.