Abstract:
The experimental results showed that due to shear drag it was not necessary for roller rotational speed to increase with camshaft speed. The lubricant viscosity played a key role in the roller sliding at lower temperatures however at higher oil temperatures negative slip was also observed indicating that component inertia and internal friction have a role to play in roller slip. Relatively, higher magnitude of roller sliding was observed for mineral oil as compared to synthetic oil having almost same viscosity while operating under similar conditions. Good lubrication conditions were also observed at cam/roller interface due to dominance of rolling motion. Increase of roller sliding with corresponding rise in oil film thickness was recorded. A good agreement between the theoretical predictions and experimental evidences was also found. It is strongly believed that the obtained realistic data will provide greater flexibility in validating the predictive mathematical models on the valvetrains and will be extremely beneficial for the engine designers and lubricant formulators in their ongoing efforts to improve the engine tribological efficiency
