Influence of Dynamic Damper Pulley Design on Engine Front Noise 2001-01-1419
Recently, there is an increasing trend to use dynamic damper pulleys for the reduction of both crankshaft vibration and engine noise.
By attachment of a dynamic damper pulley, the vibration level of a crankshaft is always significantly reduced, whereas sometimes the engine noise level shows only little reduction. The reasons are not yet understood.
For a four-cylinder, in-line type diesel engine the influence of the damper design on engine noise was investigated. Two dynamic damper pulleys which have the same torsional natural frequency but different designs were attached to the crankshaft front end. The axial vibrations of the dynamic damper pulleys were measured together with radiated noise in front of the engine, under operating conditions. The resulting noise reductions at the engine front were very different. In the worst cases, significant resonance peaks were seen at about 1KHz.
A series of experiments made the influence of the damper design clear. In addition to the design study, a rubber noise cover was developed to shield noise radiation from dynamic damper pulleys. With it, attached to the dynamic damper pulley, the engine front noise overall level in the near field was reduced by an additional 2dBA to 3dBA over the whole engine speed range.