Continental develops innovative control unit for Audi 7-speed DCT

Global supplier Continental has developed an integrated transmission control unit for the latest generation of the Audi seven-speed S-tronic dual clutch transmission (DCT) for automatic and front drive.

DCTs, which are considered one of the most significant innovations in the transmission sector, are proving popular because they offer drivers benefits in terms of fuel efficiency, smooth gearshifts and vehicle performance. The blend of sporty driving pleasure and fully automated gearshifts is also accompanied by a drop in fuel consumption compared to manual gearboxes of as much as five percent. Continental has been developing and supplying control units for (step-) automatic and dual clutch transmissions for many years now and ranks among the pioneers of this technology.

“The challenges we faced in this new control unit included packing far more functionalities into less space while at the same time ensuring that the control unit supports the outstanding fuel efficiency of this transmission, the dynamic performance it enables, and its fast shifting. Another key requirement is the functional safety of the transmission control unit, which in this particular case is implemented to ASIL-D specifications for the first time worldwide,” said Rudolf Stark, head of the Transmission Business Unit within Continental’s Powertrain Division.  “To make that possible, we have employed a new architecture and new technologies. We are proud of the fact that Audi has entrusted us with this responsible task and involved us closely in the development phase.” Series production will begin in the next few months.

More functionalities in less space

The primary purpose of the control unit is to ensure the provision of all transmission functionalities. This also involves processing a host of data served up by sensors and addressing numerous actuators.

This in turn calls for extremely close coordination of the design and functionalities of the control unit with the mechatronics of the transmission itself.

All of this has to be housed within a very restricted installation envelope. The new 7-speed S-tronic forms part of VW Group’s modular transverse matrix (MLB) and is therefore extremely compact and does not offer much room for the control unit. To further complicate matters, the new transmission control unit also handles the control of an electric transmission oil pump. Its brushless motor provides the power to supply just the right amount of oil to the dual clutch and the gear actuators. This power-on-demand concept cuts the energy requirements of the transmission. The control unit must be equipped with power components to activate the pump.  

“Owing to the lack of space within the MLB specifications we located signal-processing and power components on the same circuit board,” explained Armin Gottschaller, head of development at the Transmission Business Unit. “This meant bonding the components to a high-temperature-resistant substrate.” This Bare-Die High-Density Interconnect (BD-HDI) substrate has been specially developed by the Transmission Business Unit. “Today BD-HDI substrates are increasingly being used instead of ceramics because this way we can realise a larger number of functionalities in demanding temperature conditions,” says Gottschaller. The new 7-speed S tronic control unit, for example, operates in transmission oil that can reach temperatures of 148degC.