Impact of web and counterweight shape factors on crank shaft design for better strength and optimised geometry

Abstract

Automotive industry is continuously focusing on developing weight efficient engines for better fuel economy without altering engine performance. To achieve a trade-off between performance and fuel economy, the design always demands downsizing of engine components with optimum geometry. Crankshaft is such an important component in deciding engine performance and overall weight. Torsional and bending stiffness of crankshaft plays a vital role in its structural integrity, particularly the Critical Cross Section (CCS) which connects main journal and crankpin. In the present study, the objective is to upgrade the crankshaft for higher torsional and bending stiffness and reduce weight without changing its performance. Three geometric shape factors of the crankshaft are identified and optimized in FEA and analyzed in AVL Excite® (1-D) simulation for its structural performance. Study shows the identification of shape factors and effect of their variation on torsional and bending stiffness of crankshaft. In addition, sensitivity analysis for various shape factors and their optimization has been done. The identified shape factors help designers to identify any scope to optimize the geometry of crankshaft and understand its role in structural strength. Using this methodology, specific regions defined by shape factors can be optimized for better strength and weight.