Starter alternator in zero inertia configuration improving the functionality of the starter alternator

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Starter alternator in zero inertia configuration improving the functionality of the starter alternator

Verbakel, M.J.L. / Rondel, M. / Druten, R.M. van

The fuel economy of a vehicle equipped with an internal combustion engine can be improved by operating the engine at low rotational speeds where its optimum efficiency is found, also known as E-line tracking. However, if the engine is not oversized, this will significantly reduce the acceleration potential. An assist is then needed to guarantee an immediate response. A Starter Alternator (SA) - also known as an Integrated Starter Generator (ISG) - can replace the conventional alternator and starter motor. An additional benefit of the SA should be to provide electrical torque-assist. However, when mounted on the crankshaft in a CVT powertrain, the added inertia of the SA will take up more power during a fast downshift than the SA can deliver. This paper presents an alternative powertrain concept in which the SA is connected to the primary and secondary side of a continuously variable transmission (CVT) through a planetary gear set. In this so-called Zero Inertia configuration (ZI), the inertia of the SA will act as a mechanical torque-assist by accelerating in the opposite direction of the engine during a fast downshift. Compared to the crankshaft mounted SA, this alternative powertrain will greatly improve the acceleration response without compromising the fuel economy of a CVT in eco-mode. The SA in ZI configuration is compared on the bases of performance and fuel consumption to a standard CVT without assist, a crankshaft mounted SA providing electrical assist and the strictly mechanical ZI configuration.