The Overrunning Alternator Decoupler (OAD) is a new device for replacing the solid alternator pulley to decouple the alternator rotor inertia from the front-end accessory drive (FEAD) system. The OAD is used primarily to reduce the belt tension fluctuation in the accessory drive system when the alternator inertia, in combination with the engine torsional vibration, creates NVH (noise, vibration and harshness) problems. It is well known that the belt fatigue is very sensitive to the static and dynamic belt tensions. Additionally, the belt is also subject to sliding-wear as the belt creeps against the pulley during tension transitions. The reduced dynamic belt tension and the possibility of low preset belt tension of the FEAD system will increase the belt life and improve its durability certainly. The failures of bearing supports of components in the FEAD system are caused by high hubload level. Reduced static and dynamic hubloads on the bearings means that the expensive high grade bearing may not be required for the decoupled FEAD system. The same idea for tensioner design, due to the minor motion, the friction tensioner may not need the high quality damping material. It leads to reduce the cost of the FEAD system. Because the highest inertia of the system is decoupled, the FEAD system can work with higher level torsional vibration excitation. It permits some engines to lower idle speed in order to get better fuel consumption. In this paper, the functional principles of the OAD will be explained and the influence of the decoupled alternator rotor inertia on the performance of a four-components system (Crankshaft, Air Conditioner, Alternator and tensioner) will be reported. The test data and the numerical simulation results show clearly that the amplitude of the belt tension fluctuation, the tension arm movement and the hubload of each component are reduced significantly, when the OAD is used. This study indicates as well that the FEAD system with the decoupled alternator can work with a lower pre-set belt tension.
New technology to improve the performance of front end accessory drive system
2004
7 Seiten, 10 Bilder, 1 Tabelle, 3 Quellen
Aufsatz (Konferenz)
Englisch
New Technology to Improve the Performance of Front End Accessory Drive System
SAE Technical Papers | 2004
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