Keywords: engine front end accessory drive, overrunning alternator decoupler, OAD, rotational vibration, modelling, vehicle vibration, optimisation, dynamic performance, nonlinear vibration, simulation, spring stiffness, moment of inertia ratio, torque, alternator rotor, alternator pulley
Modelling and optimisation dynamic performances for an engine front end accessory drive system with overrunning alternator decoupler
A method for modelling non–linear rotational vibration of an engine front end accessory drive (FEAD) system is established. The FEAD consists of eight pulleys, a belt and an overrunning alternator decoupler (OAD) between the alternator pulley and the alternator rotor. Gear's method is used for calculating the rotational vibrations for driven pulleys and tensioner arm. Simulation results indicate that rotational vibrations of driven pulleys and tensioner arm, tension of each belt span, and slip ratio between belt and pulley decrease when the FEAD is equipped with an OAD. The influences of the stiffness of OAD spring, the moment of inertia ratio for alternator rotor and alternator pulley, and the torque applied to alternator rotor on the dynamic properties of the FEAD are investigated. Moreover, an optimisation model for selecting OAD design parameters to minimise rotational vibration of tensioner arm, slip ratio between belt and a pulley is proposed. The optimised result validates the presented optimisation method.