Graziano Transmissions
of Italy is developing a 750Nm dual clutch transmission (DCT) for supercars.
The programme for a European OEM is in prototype phase, aiming for production
in 2010.
The firm supplies automated manual transmissions (AMTs) for very high
performance brands including Ferrrari, Maserati and Aston Martin. Fast
cars need fast gearshifts but keeping up with OEMs’ requirements
has brought AMT technology to its limits.
Graziano’s head of automotive transmissions Paolo Mantelli said:
“Shift times below 60ms put components such as forks and synchros
under great stress. We needed a radical change in the base transmission.”
Shift quality is also why the popularity of AMTs is waning. As shift times
reduce, they can become jerky. Issues with the “comfort” mode
of the Quattroporte’s AMT led to Maserati adding a six- speed ZF
automatic. DCTs combine the advantages of both types and shift performance
can be tuned.
Cost is an issue. “Our target is to cost no more than an AMT, but
at low volumes this is a challenge,” Mantelli said. He wants to
develop the technology into a flexible, scalable solution for mid-engine
and front engine/rear-transaxle layouts.
The gearbox is a seven speed, three-shaft design. It uses wet clutches
because dry clutches can’t cope with the heat from repeated launches.
Designing a DCT requires expertise in mechanics, hydraulic actuators,
electronics and software. Graziano has an edge here. It is majority stakeholder
in control specialist Vocis and is using its TMS-20 controller during
development.
The firm is also working on packaging a torque-vectoring final drive into
a transaxle, and a fully electrically-operated AMT for Asia’s medium
commercial vehicle market that is cheaper and smoother than conventional
AMTs.
Mantelli says growing congestion in Europe will help drive DCT as the
smooth shifts suit city driving. “Fuel economy will also create
demand for DCT in the US,” he said. “Drivers want the comfort
of an automatic but with better efficiency.”
The firm expects initial volumes to be up to 6,000 units.
© Automotive Engineer, 2007
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