Valeo is highlighting its two micro-hybrid systems—the i-StARS belt-driven starter-alternator (earlier post) and ReStart, a reinforced starter—for the US market. Both solutions enable stop-start functionality and can help reduce the fuel consumption of a traditional internal combustion engine by 2-3% during the standard driving cycle and by up to 15% in congested urban traffic.
Valeo launched its first belt-driven starter generator on the Citroen C3 in 2004 and programs with Mercedes, Nissan and PSA followed. In 2010, it launched its second-generation starter-generator system (i-StARS) on Peugeot and Citroën brands. (Earlier post.) Valeo is leveraging this experience in reversible belt-driven machine design in its development of higher-voltage belt-driven systems for mild hybrid applications. Valeo says that its next generation of systems will have the ability to recover braking energy and provide engine torque assistance.
During the United States CAFE urban test cycle, a car is idle about 19% of the time or 10% for combined highway/city operation. Making automatic engine shut-down and restart more affordable is a viable near-term solution to reducing vehicle CO2 emission and improving fuel economy.—Valeo Group Product Marketing Director Derek de Bono
i-Stars. Valeo’s i-StARS (integrated Starter Alternator Reversible System), is a stop-start system based on a combined starter-alternator solution replacing the conventional alternator. Similar to an alternator, it is linked to the crankshaft through the belt drive. i-StARS enables the combustion engine to shut off when the driver begins to brake and the vehicle has dropped below a preset speed. For example, one Valeo application example in the market today stops the engine when the vehicle speed drops below 5 mph (8 km/h) for automatic transmissions and below 13 mph (20 km/h) for manual transmissions. i-StARS automatically restarts the engine in approximately 400 milliseconds, even when drivers unexpectedly change their minds during stopping sequences.
i-StARS is a 14-volt LIN-interfaced, belt-driven starter-alternator with integrated electronics that is scalable up to 8 kW. Compared to previous product generations, the advanced design provides increased torque and reliability, while improving cost, packaging and temperature management. In addition to LIN, it can interface with any OEM engine control unit architecture, such as RVC and C-Terminal.
As the vehicle’s alternator, i-StARS’s power electronics improve the system’s electrical efficiency to make it one of the most efficient alternators on the market. The integrated control and power electronics reduce system cost and makes it easier to install during vehicle assembly, Valeo says. The i-StARS+ version is a seven-phase design, making it extremely quiet. It can be applied to up to 4-liter gasoline and 3-liter diesel engines and easily adapts to both manual and automatic transmissions.
The i-StARS belt drive enables a faster and smoother engine stop with less oscillations and a smooth and silent restart. Ready for automatic transmission applications, the innovation’s belt drive offers greater stop-start functionality by making it possible to restart an engine while the flywheel is still rotating or the gear is still engaged. Allowing the engine to stop before the vehicle does, maximizes the fuel economy benefits of a vehicle coasting to a stop. This capability makes it suited for the United States market, where more than 90% of vehicles are equipped with automatic transmissions and drivers expect smooth and silent start-stop operation, Valeo suggests.
ReStart. Valeo’s ReStart reinforced starter provides extra durability for repeated stopping and starting when the vehicle comes to a complete standstill. ReStart has minimal impact on engine architecture and can be applied to a variety of engine types and displacements.
Currently, Valeo is developing a reinforced starter capable of restarting an engine, while it is still rotating, for automatic transmissions and to offer additional fuel economy improvement.