| A Serpentine Belt Accessory Drive system (SBAD) with an automatic tensioner iswidely used to drive all accessory elements. The tensioner maintains constant tractive tensionof the belt spans adjacent to it. The advantages for a SBAD including compactness, highpower, length of belt life etc. Since1970, SBAD is widely used in the engine Frond EndAccessory Drive system (FEAD). The design ability of FEAD in China and the application ofFEAD in the domestic-made automobiles are in the initial stages, it is urgent that the designmethods and techniques of FEAD are studied extensively and systemically. To achieve thegoals, the research work of this dissertation includes:1. Longitudinal static stiffness, longitudinal dynamic stiffness, damping coefficient andbending rigidity of serpentine belt, and friction coefficient between belt and pulley arethoroughly tested. Experimental methods and data processing techniques for theseexperiments are presented. A serpentine belt with six ribs and a K-rib section (6PK) is takenas test belt in the experiments. Two experimental setups, MTS831servo-controlled hydraulictest rig and shock hammer, are used to measure the properties of belt longitudinal dynamicstiffness and damping coefficient. Two models of polynomial function and exponentialfunction are presented for modeling belt longitudinal dynamic stiffness and dampingcoefficient, respectively. Parameters of the two models are identified by the optimizationprocess in the least-squares sense. Then, the influences of the belt length on the belt bendingrigidity are measured and investigated. Moreover, the influences of wrap angle between beltand pulley, pre-tension of belt and rotational velocity of pulley on the friction coefficient aremeasured and analyzed, and the ranges of the friction coefficient are obtained.2. Experimental methods and data processing techniques of the static and dynamicproperties for FEAD are presented, and the parameters to evaluate the performance of FEADare discussed. The static and dynamic properties for an eight pulley-belt FEAD are tested inthis paper. The static tension of belt, rotational vibrations of driven pulleys and tensioner arm,hubload of tensioner pulley, and transverse vibration at the midpoint of belt span are measured.The dynamic tensions of the two belt spans adjacent to tensioner pulley can be indirectlycalculated with its dynamic hubload of measurement. The slip ratio between pulley and belt can be estimated by the relative velocity between pulley and belt divided by the belt velocity.The influences of belt pre-tension on the dynamic properties of the FEAD are measured andcompared when two serpentine belt of different length are used in the FEAD.3. Unified formulae for modeling rotational vibration of a FEAD are presented, and ageneral purpose software for calculating rotational vibration is developed based the presentedunified formulae. In modeling of a FEAD, the damping and stiffness of a belt are regarded asthe function of excitation frequency of an engine and amplitude of belt stretching. Also thecreeping effect of a belt on pulley wrap arc is included in the model. An eight pulley-beltFEAD is taken as studying example to demonstrate the unified formulae and the procedure forobtaining rotational vibration. The static tension and steady-state tension of each belt span,natural frequency of the FEAD, rotational vibrations of driven pulleys and tensioner arm,dynamic tension of each belt span are calculated and compared with experimental data.Moreover, the influence of belt creeping on the dynamic characteristics for the FEAD isestimated and investigated.4. A mathematical model for nonlinear rotational vibration analysis of an eightpulley-belt FEAD equipped with an Overrunning Alternator Decoupler (OAD). The OAD isequipped between the alternator pulley and the alternator rotor. Gear's method is used forcalculating the dynamic characteristics of an eight pulley-belt FEAD with or without an OAD.The influences of the stiffness of OAD spring, the moment of inertia ratio for alternator rotorand alternator pulley, and the torque applied to alternator rotor on the dynamic properties ofthe FEAD are investigated. Moreover, an optimization model for selecting OAD designparameters to minimize rotational vibration of tension arm, torque of OAD spring and slipratio between belt and alternator pulley is proposed. The rotational vibrations for pulleys andtensioner arm, and slip ratio between belt and alternator pulley are calculated with theoptimized variables and initial variables. |
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