Suppliers Target the ?500 Dual Clutch Transmission

Interest is growing among suppliers and automakers for low-cost dual clutch transmissions aimed at big-selling family cars and vehicles destined for emerging markets.

Leading transmissions supplier Getrag, which already provides DCTs under the PowerShift label to Ford, Volvo and other automakers, has embarked on a project to develop a low-cost system with a target price of ?500 ($680), while BorgWarner, pioneer supplier of clutches (and components) to Volkswagen Audi, is well advanced with the development of its own low-cost system, dubbed the DT170.

Both BorgWarner and Getrag stress the importance of reducing the cost of the transmissions’ ancillary systems such as the actuators, the sensors and the electronic control mechanisms. Also in this area, UK-headquartered engineering services provider and specialist transmissions manufacturer Ricardo is finalizing development of a low-cost eDCT transmission which dramatically simplifies the actuator design and operation.

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The Ricardo system is based on patent-pending linear electromagnetic actuator and control technology which combines clutch operation and gear selection into a single duplexed unit for each of the two clutches. This technology has already been demonstrated by Ricardo using a single multiplexed actuator in an AMT vehicle: in benchmark step tests carried out against a current production hydraulic valve actuated system, Ricardo claims its system is in excess of eight times faster.

With the new dry clutch transmission nearing completion, Ricardo says eDCT will provide a high efficiency, zero torque interrupt transmission system which, based on the results of simulation and component testing, will provide a fuel consumption saving of in the region of 5 percent in comparison with a hydraulically actuated wet clutch DCT.

Ricardo says it is aiming to unveil an eDCT based demonstrator vehicle in the spring of 2009.

Alexander Moser, lead analysis engineer at BorgWarner Drivetrain Engineering in Germany, believes the fuel-saving potential of DCTs will make them a very cost-effective proposition for all sizes of vehicle. “We see particularly attractive applications on low-cost cars,” Moser told DCTfacts.com at the CTI transmissions symposium in Berlin last month. “We expect to have these systems in production by 2010 or 2011.” Prototypes of the DT170 were already running, said Moser, and it would be comparatively straightforward to offer six- as well as five-speed versions.

At Getrag, says systems engineering manager Christian Krauss, the proposed LCDCT120 would save cost by operating independently of any engine interface and with the minimum number of actuators. “For a low overall cost of the complete system we need to look closely at the sensors and the actuators.” That, Krauss told DCTfacts.com, is where the real cost-saving opportunities are to be found:“Every transmission will need a gearset. They will all need a clutch system, too. The overall system cost is really determined by the sensors, the actuators and the computation power you require.”

Each sensor or actuator adds a finite chunk, says Krauss, so if you have a clever system which gets around actuation and sensing, it will be cheaper, irrespective of whether it has a dry or wet clutch.

Clutch choice

Given that low-cost DCTs will be targeted at entry level models, generally powered by gasoline engines with relatively low torque outputs, it would initially appear surprising that both the Getrag and BorgWarner designs reject the idea of the dry clutch, often thought to be the simplest solution.

Krauss makes the point that drivers may have to rev up a small gasoline engine harder to access the torque band for a steep hill start, meaning possible thermal capacity issues for a small dry clutch; at BorgWarner, Moser believes that the heat dissipation capacity of a dual wet clutch’s oil system could allow automakers to use simpler and cheaper gasoline engines, thus further reducing the cost of the overall vehicle.

Repeated launches, such as when inching forward in traffic, could easily overheat a simple dry clutch system, says Moser.

BorgWarner’s DT170 saves costs in other important ways, too. Instead of mounting different-sized clutches concentrically, it uses two identical clutches mounted alongside one another, linked by a chain; this helps keep the transmission length short and allows easy changes of overall ratios to suit different categories of vehicle. The clutches themselves can be smaller and less costly as they rotate at less than engine speed. Further cost savings are achieved by the elimination of the synchronizer and actuator for first gear, an idea which BorgWarner says could be applied to other DCTs too.

Other simplified components include the input shafts, the synchronizers and the reverse idler, and the fact that the internal gears will be common to all applications and derivatives produces yet more savings.

Just how much all these saving add up to is, however, not a topic BorgWarner is yet prepared to discuss. Questioned, Alexander Moser was less forthcoming on whether BorgWarner could match the ?500 cost targeted by Getrag, saying that it was in negotiations with several automakers and that one possibility was that in genuinely low-cost cars the DCT could be the only transmission offered, thus disguising its cost to the consumer.

“In future, it might not be an option – these cars might always be sold with automatic transmission like a DCT,” he said. “For example, if you had the start-stop function, where you can save 6 to 7 percent on your fuel bills, the driving would be much more comfortable with automatic operation.

All the driver has to do is press the throttle and drive away.”

Fittingly, BorgWarner has also developed a clever mild hybrid solution which eliminates the need for the mechanical first and reverse gears in the DCT; these functions are performed exclusively with the electric motor. Only on very steep hill starts is the e-motor supplemented by power from the combustion engine.

Manufacturing

Both suppliers stress the importance of the manufacturing process in ensuring low-cost DCTs approach the entry-level car market in the most effective way.

BorgWarner is reticent when it comes to manufacturing specifics but, says Moser, it prefers to concentrate on what it knows best. “Our main focus will be on the modules – the clutches, the chain, the dampers, the controls module, the synchronizers. The other areas will be handled with a partner or through a joint venture.”

This is a continuation of the group’s strategy to supply clutch modules to other transmission makers – including Getrag – as well as to automakers. “there are already a lot of conversations going on,” he says enigmatically.
BorgWarner CEO Timothy Manganello last year predicted global DCT sales of 5 million units by 2013. This, equating to a market share of around 6 percent, is a more bullish forecast than those presented by most analysts: almost certainly, it must reflect high expectations for the strong acceptance of BW’s low-cost DCT in the entry-level sector across a broad range of markets.

Work on Getrag’s LCDCT120 is not at such an advanced stage as BW’s design, admits Christian Krauss, but again the manufacturing process is an important element of the overall concept.

“The idea is to rearrange the design of the transmission so that we can get down to the bare minimum in terms of actuators,” he says, hinting that there will be genuinely radical steps to “really getting the cost out.”

Large sales volumes are not crucial to Getrag’s low-cost DCT concept, says Krauss. Getting down to the “realistic” target of ?500 means a degree of volume sensitivity, he says, “but not in the sense that we would need to produce, say, a million a year to get down to that figure.”

“The low cost DCT not a transmission that would be completely suited to applications where perfect shifting is important,” explains Krauss. “It [the Getrag low-cost concept] is targeted for low cost, and if you look at the low-cost segment you will find completely different border conditions with respect to engine control systems. That has to be taken into account when you define this type of [transmission] system.”

With the transmission being targeted at emerging markets, one of the development targets is that it should be possible for the systems to be produced not just in the traditonal fashion in Germany but “anywhere” – that is to say in emerging markets and countries with less of an industrial heritage. The plan, as with BorgWarner, is to enter into collaboration with an automaker to bring the transmission into volume production: Krauss declined to be drawn on likely partners or start of production dates, saying that the project was “still too fresh.”

One way or another, however, the prospects for low-cost DCTs look rosy. The system’s proven ability to boost comfort and save CO2 will find an enthusiastic audience in the entry-level sector as long as the additional cost is kept low. It remains to be seen whether with its innovative design Getrag can hit its ambitious ?500 cost target, but in the more immediate future BorgWarner appears very confident it can gain significant early-mover advantage, particularly in the entry level segment where affordable automatic transmissions are rare or non-existent.

And with the economic downturn refocusing buyers’ attention on lower-cost vehicles, better fuel economy and simpler driving routines, the time for clever transmission thinking has clearly arrived.