Fraunhofer tips cap

Researchers at the Fraunhofer Institute have developed a device using shape-memory metal that could greatly simplify the mechanism used to automatically open car fuel-filler caps.


When drivers press the dashboard control using current systems, it triggers a small servomotor, several cogwheels and various springs – more than 10 separate parts in all. In Fraunhofer’s design, a single wire made of shape-memory material will be sufficient to open the release mechanism for the fuel-filler flap.


When shape-memory constructs are made, they can be deformed and regain their designated shape when heated, exposed to a magnetic field or held up to the light.


Dr Gunther Naumann, team leader at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Dresden, said: ‘We pass a current through the wire and it heats up. The heat causes it to remember its original shape, so it contracts and opens the filler cap.


‘Our release system has several advantages. It is on average 80 per cent less expensive than conventional systems. We can also save about 90 per cent of the weight, as the special wire only weighs five grams.’


The release system is also much smaller. The housing of the usual servomotor takes up a space of 6 x 4 x 3 centimetres, but the wire can be integrated in the existing tie rod, taking up no extra space.


A prototype of the system has already been built, using an off-the-shelf nickel-titanium alloy, which is already ‘trained’ to contract when heated.