Modeling and Analysis for Dynamic Performances of a Two-Layer Engine Front End Accessory Drive System with an Overrunning Alternator Decoupler

Two-layer engine front end accessory drive systems (TEFEADS) are adopted generally by commercial vehicles due to the characteristics of the accessory pulleys, which have large torque and moment of inertia. An overrunning alternator decoupler (OAD) is an advanced vibration isolator which can reduce the amplitude of torsional vibration of alternator rotor effectively by an one-way transmission and they are more and more widely used in vehicles. This paper established a model of a generic layout of a TEFEADS with an OAD. The coupling effect between the TEFEADS, the nonlinear characteristics of OAD, the torsional vibration of crankshaft and the creeping on the belt were taken into account. A nine pulleys model was provided as a study example, the dynamic responses, which are respectively under steady and accelerating conditions, of the system were calculated by the established method and compared with the bench experiment. The influence of different belt material, the stiffness of OAD spring and the parameter of the tensioner on dynamic performances, such as the oscillation of tensioner arm and the dynamic belt tension were analyzed.