European interest in dual-clutch technology shifts up a gear
Although automatic transmissions are gaining a greater market share, especially in northern Europe, consumer resistance remains strong. Europe's skeptical consumers, however, may be persuaded to change by the new dual-clutch transmissions. Matthew Beecham reports.
Of the three main vehicle markets of the developed world, Europe remains unique in that nearly 80% of passenger cars are sold with manual transmission. Motorists with an interest in performance prefer changing gear for themselves, while those more concerned with economy still believe that—quite apart from their extra cost—automatic transmissions deliver inferior economy.
The direct shift gearbox, powershift gearbox, twin-clutch gearbox are just a few of the terms used to describe the dual-clutch gearbox. The gearbox concept combines the advantages of a conventional manual shift with the qualities of a modern automatic transmission. It originated in motor sport and is characterized by having two part gearbox units, which operate the odd and even gears, respectively. It means that when changing gear the engine torque is transferred continuously from one gear to the other. The result is gentle, jerk-free gear changes with the same relaxed driving style found in an automatic combined with the efficiency of a manual transmission.
The VW Group pioneered dual-clutch technology and continues to push it in the European market. BorgWarner played a key role in the development of VW's DSG 6-speed automatic gearbox, which combines the smoothness of a state-of-the-art torque converter with the fuel efficiency of a lighter and cheaper to manufacture 6-speed manual. "Our DualTronic will continue to feature in VW front-wheel drive cars as well as gradually penetrate into different market segments," said Bernd Matthes, President and General Manager of Borg Warner Transmission Systems about the company's DualTronic transmission system. "There are no limits or technology barriers. It has a broad application range covering the entire vehicle market."
BorgWarner predicts that demand for the technology will grow from nothing today to a quarter of the European passenger car market by 2014, and will give it a foothold in the US and Japanese markets during that time. "By 2014, we see dual clutch transmissions capturing 25% of the European market," said Matthes. "It will serve as a replacement for the traditional automated manual transmissions, CVTs and traditional planetary type automatics. With the trends towards more automation in Europe, we see replacement of pure manual transmission."
Matthes believes there were a number of key technology advances which made the production of the dual-clutch transmission possible. He said: "Let's start with the clutch itself. Over the past few years we have made some major advances to the friction material such as improving heat resistance. Also, there have been improvements in oil which, together with the friction material, provide a system that is more stable under the certain conditions. There have also been some advances with the control module. Over the last decade, the electronic control module has become more powerful and yet cheaper. For the DualTronic we also developed a special type of solenoid for more precise clutch control. So electronics and solenoids on the control side as well as improved friction materials and oil have been the key technology breakthroughs."
BorgWarner is still the only player in the dual clutch market although other manufacturers are set to enter it. "Our customers will clearly not allow us to be the only players in this market," said Matthes. "But the main competition that is taking place right now is not so much between us and other players but between the wet clutch technology - which we favour because it is more robust, easier to handle and has a wider application range - and dry clutch technology. The dry clutch manufacturers such as LuK, ZF Sachs and Valeo are developing their own solutions. We will see some of those in the future on the lower end of the vehicle lines. But I do not see those coming into mid-size vehicles or even larger compact vehicles. There is a clear border line when it comes to torque capability and functionality. On the wet clutch side, we are still the key player and I would assume we shall remain so for the foreseeable future. Whereas the others are now working on their first generation, we are now working on our second generation. "
LuK is also working on its dual-clutch transmission solution. The company began work on this area in 2003. LuK refers to it as a 'parallel shift gearbox'. "Depending on the application, we can offer our customers designs for the wet or the dry version," said Dr Wolfgang Reik, head of LuK's R&D department. "On the basis of the development projects underway at present, we believe that the clutch could be part of mass-production by the end of 2007."
Although LuK has already shown a dry clutch version of its dual-clutch transmission, the German supplier is keeping its options open. Reik added: "We are quite certain that the wet twin clutch offers advantages in some circumstances for specific applications. For example, where particularly high torques are present and we are therefore working in parallel on developing both designs." The company says it can supply both wet and dry clutches depending on the OEM's requirements.
Meanwhile, Continental Automotive Systems has developed a control unit for a dual-clutch transmission which entered production in 2003. The company is bracing itself for a booming market. "Right now we are running five separate development projects for future automatic transmission. Four of the resultant control units will form part of double-clutch transmissions," said Bernd Stockmann, manager of the company's transmission profit centre within the Chassis and Powertrain business unit.
Stockman says the obvious fuel savings should fuel demand. He said: "The percentage of fuel saving is very much depending on the compared engine/transmission combination. A rough number is somewhere between 5 to 10% fuel saving compared to an automatic transmission. The fuel consumption of a DCT is somewhere in the area of a vehicle with manual transmission. DCT in combination with a diesel engine shows a big improvement in the area of vehicle launch performance, known as the 'rubber band effect', caused by the torque converter, which is known in combination with step automatic transmissions can be eliminated due to the double clutch concept." The company's dual-clutch transmission control unit is currently available on the VW Beetle, Golf, Touran, Passat, Jetta, Golf Plus, and Caddy; Audi TT and A3; Skoda Octavia; and Seat Altea, Toledo, and Leon.
Other carmakers are trying to catch up. Ford is the second major carmaker to commit to dual-clutch transmissions.