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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 generator is an important loaded component of an engine front end accessory drive system (EFEADS). With a huge moment of inertia and a highest running speed, the vibration and noise often occurs in operation, which has an effect on the service life. Thus an overrunning alternator decoupler (OAD) is used in the EFEADS for reducing the vibration of system. In this paper, a model of EFEADS with an OAD is established. The impact of the OAD on the dynamic responses of pulley of generator and the system are analyzed, and is verified by bench experiments. And the influence of parameters, such as spring stiffness, moment of inertia of generator and loaded torque on the dynamic performances of the system are studied. The influence of misalignment in pulleys on the dynamic performance of system is also discussed. The presented method is useful for optimizing the dynamic performance of system, such as the oscillation of tensioner arm and the slip ratio of the belt-generator pulley.

A model for a generic layout of an engine front end accessory drive system is established. The dynamic performances of the system are obtained via a numerical method. The dynamic performances consist of the oscillation angle of tensioner arm, the slip ratio of each pulley and the dynamic belt tension. In modeling the system, the hysteretic behavior of an automatic tensioner, the loaded torque of the accessory pulley versus the engine speed, the torsional vibration of crankshaft and the creep of the belt are considered. The dynamic performances of the system at steady state and under accelerating condition are analyzed. An example is provided to validate the established model. The measured results show that the torsional vibration of crankshaft is larger and the dynamic performances of the system are different under accelerating conditions, though the acceleration is small.

The automatic tensioner is an important component of the engine front end accessory drive system (EFEADS). It maintains the tension of the belt steadily and reduces the slip of pulley, which is benefit for improving the life of V-ribbed belt. In this paper, an EFEADS model is established which is considering with the hysteretic behavior and the asymmetry of friction damping of a tensioner. A four-pulley EFEADS is taken as a study subject. The dynamic responses of system, such as the oscillation angle of each pulley, the slip factor of pulley, the oscillation of tensioner arm and the dynamic belt tension are analyzed with symmetric damping and asymmetric damping tensioner. Meanwhile, the influence of asymmetric damping factors of tensioner on the dynamic response of EFEADS is also investigated.