The Challenges Of Start-Stop Technology

Whatever vehicle manufacturers (VMs) choose to label them, there is no question that the number of vehicles that feature Start-Stop technology will continue its dramatic rise over the next few years. As it stands, it is only by incorporating a Start-Stop function into a certain number of models in each range, that the VMs will be able to reduce their fleet average emission levels and achieve the targets that EU legislation demands.

However, the development of the technology has required their component suppliers to push their research and design teams to the limit to come up with the required solutions and deliver the final Start-Stop systems.

Some VMs have opted for an uprated starter motor to cater for the far greater number of engine starts these vehicles need, whereas others have opted to use a starter/alternator driven by a belt to provide a faster, quieter engine start. The starter/alternator combines both a starter motor and an alternator into one component, which is able to switch between each function on demand.

For Dayco, in its alliance with Peugeot/Citroën (PSA), a starter/alternator was the chosen solution and so the challenge was to engineer an auxiliary belt system with the strength to start and restart the engine instantly when the vehicle needs to pull away, but that was no wider than a standard auxiliary belt.
This objective was extremely difficult to achieve, the increased stresses generated through the starter could have made it necessary to use a belt twice as wide as normal However, at the conclusion of the complex project Dayco had developed a belt of a traditional width, coupled with a tensioning system able to maintain the correct tension on the belt and allow power to be transmitted in either direction, depending on whether starting the engine or driving the alternator.

In contrast to a conventional belt system, the patented Dayco Self Tensioning System (STS) maintains a balanced tension on both sides of the belt in relation to the starter/alternator drive pulley. Instead of having a tensioner on just one side of the belt system, the tensioning device connects both sides of the starter/alternator belt system.
Dayco STS, is designed to create a balance of forces between the two sides at all times, which enables the starter/alternator to seamlessly switch between its starting and charging modes to allow the vehicle’s Start-Stop system to function to its full potential.

The cornerstone development of this self-balancing device is the rigid connection of its pulleys, which allows it to maintain the correct belt tension irrespective of the direction of the load. It is an excellent example of how challenging objectives can bring out the best from component manufacturers that need to work with VMs to find the best design solutions and which therefore defines them as world leaders in technology.