NVH Analysis of Balancer Chain Drives with the Compliant Sprocket of the Crankshaft with a Dual-Mass Flywheel for an Inline-4 Engine 2007-01-2415

The work presented in this paper outlines the design and development of a compliant sprocket for balancer drives in an effort to reduce the noise levels related to chain-sprocket meshing. An experimental observation of a severe chain noise around a resonant engine speed with the Dual-Mass Flywheel (DMF) and standard build solid (fixed) balancer drive sprocket. Torsional oscillation at the crankshaft nose at full load is induced by uneven running of crankshaft with a dual-mass flywheel system. This results in an increase of the undesirable impact noise caused by the meshing between the chain-links and the engagement/disengagement regions of sprockets, and the clatter noise from the interaction between the vibrating chain and the guides.

This paper evaluates and discusses the benefits that the compliant sprocket design provided. A multi-body dynamics system (MBS) model of the balancer chain drive has been developed, validated, and used to investigate the chain noise. This analytical model describes the entire balancer drive system coupled with a full cranktrain system. The balancer drive system contains a chain drive, balance shafts, and a water pump shaft. The cranktrain system contains a crankshaft, piston, connecting rod, and a dual-mass flywheel. For subjective noise assessment, simulations of a solid sprocket versus compliant sprocket balancer drive with both Dual Mass and Conventional Flywheel were carried out and compared. Whine metrics on sprockets and impact patterns on guides and sprockets are presented in this paper to provide a tool set toward designing a quiet chain drive system.