Dynamic analysis of a front-end accessory drive with a decoupler/isolator

In automotive front-end accessory drives (FEAD), the crankshaft supplies power to accessories like alternators, pumps, etc. When the FEAD undergoes forced vibration due to crankshaft excitation, dynamic tension fluctuations can cause the belt to slip on the accessory pulleys. In this paper, an accessory inertia (e.g. alternator) is isolated/separated from the FEAD by placing between the pulley and accessory a combination of a one-way rigid clutch and an isolator spring. The rotational response of a typical FEAD is extended to include this decoupler-isolator. Analytical solutions are obtained by considering it as a piecewise-linearised system about the equilibrium angular displacements. The tension fluctuation of the ordinary FEAD is then compared to that of the system with a decoupler/isolator. The results indicate that within the practical working range of engine speeds, use of either an isolator or a decoupler-isolator could significantly lower the dynamic tension drop across the accessory pulley.