NVH Research On Engine Front End Accessory Stretchy Belt Drive System

The vibration of Front Engine Accessory Drive(FEAD)system directly comes from engine’s crankshaft,hence the torsional vibration of the engine will go to the FEAD system through crankshaft,therefore the performance of the FEAD system will impact the driver’s comfortable.This thesis is to propose the stretchy belt FEAD system through the design change of the tensioner FEAD system based on one specified engine.The design and validation in this thesis will focus on the NVH performance of the stretchy belt FEAD system by both analytical simulation and physical validation.Meanwhile,the fitting tool for the stretchy belt installation will be modified through ergonomics study and it finally meets the manufacturing criterion.This thesis detailed described on the following items,and they are the key points that related with stretchy belt FEAD system design and optimization:To correlate the engine firing frequency,engine speed,the number of the engine cylinder with Fourier transform.It gives the relationship between engine speed and torsional vibration.Detailed specify the belt tension and belt coefficient of friction on the contribution to avoid the belt slippage and FEAD system noise by using Euler theorem.In order to isolate the resonance of the FEAD system,this thesis establishes single freedom spring system mechanism mode and applies it to the biggest inertia rotation component,then proposes to select the desired spring rate to shift the natural frequency of the FEAD system as the successful solution to FEAD system resonance.To simplify and optimize the FEAD system by deleting the previous tensioner with the replacement of the stretchy belt system by both static and SimDrive3 D dynamic FEAD system simulation and calculation.Its outcome is the belt flapping,belt slippage,and the hubload to each pulley.Also the fatigue of the FEAD component with new FEAD system is also accessed with finite element analysis.Validation like FEAD characterization,cold start and water wadding is performed as physical validation to further validate the robustness of the new designed FEAD system,and the physical validation meets the dynamic simulation results.Belt slippage is acceptable and there is no audio noise detected under server scenario.Some audio sensors are installed inside the car cabin to collect the articulation index input,and the stretchy belt FEAD system is found with better AI value compared to tensioner FEAD system.