Optimisation of vehicle operation contributes to a reduction in "fleet fuel consumption", such as internal engine measures. The introduction of an automatic start/stop mechanism represents an important step in the right direction.
Of the large number of different approaches to solving the problem that have been investigated in order to realise an automatic start/stop mechanism, the belt-driven version of starter generators is an extremely interesting alternative in relation to comfort, performance and cost. The new generation of electrical components is available to the vehicle manufacturer in various power ratings and efficiency has been considerably improved. The application spectrum extends from simple "low cost" systems for conventional 14 V vehicle electric systems to a "high end" solution for future 42 V systems. Starting from a simple "start/stop version" and extending to the high performance system with expanded functionality, a range of different customer-specific solutions can be achieved. The integration of a "boost" function, combined with the possibility of regenerative braking, offers additional potential savings. An economical and effective entry into hybridisation of vehicles is thus within much closer reach for the vehicle industry.
The driving force for the introduction of start/stop functionality is ultimately the aim of achieving the emission limits agreed for 2008. Due to the direct relationship between CO2 output and fuel consumption, the target limit of 140 g/km can also be expressed as a mean consumption. Mathematical conversion means that, for 2008, the required mean consumption for petrol engine vehicles will be approx. 5,7 l/100km while diesel engine vehicles will be able to consume approx. 5,1 l/100km. Compared with consumption figures from 2002, which averaged ~7 l/100km, this means a required saving of between 20% and 25%. This objective represents a major challenge for the whole automotive sector and affects vehicle manufacturers and suppliers in equal measure.
x: Development of fuel consumption
y: Fuel consumption [l/100 km]
Figure: Development of mean fuel consumption (source: VDA)
The introduction of a start/stop function offers, as a function of the selected drive cycle, an additional potential saving of between 5% and 10%. The starter generator in the belt drive thus makes a considerable contribution to the successful implementation of the 2008 goals.