VS - Electrical Systems From Stop-Start to Hybridization

Engine downsizing and acyclisms level

Fuel saving needs and environmental regulation (Euro4/5/6) have pushed all car manufacturers to apply downsizing techniques to engines. Downsizing consists of reducing the cubic capacity while maintaining the engine’s level of performance. This is basically done with turbocharging and high pressure direct injection, further downsizing can be achieved with powertrains electrification. Downsizing has a direct impact on acyclisms levels increase; this phenomenon is even more sensitive on 3 cylinders applications. High acyclisms levels have lead to a massive use of coupling devices to protect the auxiliaries’ driveline. Similarly, the clutch system had to face the same filtration problem for the gearbox! While recent generation of alternators benefit from freewheel pulleys to absorb increasing engine torsional vibrations, belt starter generators machines can't, they manage positive or negative torque, forbidding the use of any freewheeling device. The latest generations of so called decoupling tensioners have the ability to absorb part of engine torsional vibrations, they are supported by crankshaft damper pulleys. Single stage BSG tensioner Though BSG tensioners requires theoretically a dual stage systems, in the very first Micro-Hybrid applications as the Smart Fortwo MHD, the Citroen C2/C3 and the Mercedes A/B-Class 1.5L and 1.7 gasoline engines, some single stage tensioners have been used. This was made possible either by the engine reduced capacity (cranking torque up to 35Nm) or by a more complex serpentine belt drive for Daimler applications, nevertheless these single BSG tensioners were more sophisticated than conventional ones.

Freewheel pulleys can not be applied to BSG machines

Smart fortwo tensioner

Smart fortwo tensioner

Citroën C2/C3 tensioner

Citroën C2/C3 tensioner

Mercedes B-Class tensioner

Mercedes B-Class tensioner

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