|The Valeo StARS belt-driven starter generator replaces a conventional alternator.|
At the Frankfurt IAA, Ford indicated that it is considering combining a belt-driven integrated starter generator (B-ISG) with its Duratorq 2.0-liter TDCi diesel engine. The Ford Focus and the C-MAX both feature the engine, and Ford believes that it is this segment in which such micro-hybrids would be the most appreciated by customers.
Ford has worked on several micro-hybrid prototypes, both with a Valeo StARS (Starter Alternator Reversible System) unit in the B-ISG system. One is the 1.4-liter micro-hybrid Fiesta, announced last September; the other, the 2.0-liter HyTrans commercial van (earlier post).
Micro hybrids feature stop/start functionality, regenerative braking, and electric systems efficiency, but offer no electric propulsion support.
(The Belt Alternator Starter mild-hybrid system GM will apply to the Saturn VUE next year (earlier post) does provide occasional motive assistance during acceleration.)
With the major limitation of offering no such propulsion support, micro-hybrids deliver small improvements in fuel economy under mixed driving conditions—some 5% improvement, by Ford’s estimate.
However, in heavy stop-and-go traffic, this figure can increase to as much as 15%, or possibly higher depending upon the driving pattern. In the work on the HyTrans van with its research partners Valeo, Ricardo and Gates, for example, Ford found that the micro-hybrid increased fuel efficiency by 21% in the urban delivery cycle (one that involves a lot of stopping, idling and so on.)
Citroën introduced a Stop&Start version of its C3 last year using the Valeo system, with reductions in fuel consumption of between 6%–15% (but no regenerative braking). (Earlier post.)
|The core B-ISG system from Valeo|
Ford’s B-ISG micro-hybrid system combines automatic stop-start engine operation and regenerative braking, controlled by an advanced battery management system.
The core of the system is Valeo’s 14V StARS starter generator. An inverter is placed between the battery and the conventional belt-driven machine to allow both quick starter and efficient alternator operation, and the management of the start-stop strategy. Electronic control and belt drive allow to engine restart within 400 milliseconds—three times as fast as a conventional starter.
In alternator mode, the system is 20% more efficient than a conventional unit thanks to its MOSFET (metal-oxide semiconductor field-effect transistor)-based design. Both generator and electronics are air cooled.
Valeo is developing regenerative braking capacity for its system.