NexxtDrive DualDrive e-CVT Prototype Promises Fuel Savings, Hybrid Capability
14 September 2005
|NexxtDrive’s DualDrive Transmission|
NexxtDrive (formally DriveTec UK), a UK-based design and development company, used the Frankfurt IAA to promote its prototype DualDrive, a power-split electronic Continuously Variable Transmission (e-CVT) with dual motor-generators.
NexxtDrive claims that the DualDrive can provide potential fuel and CO2 emissions savings of up to 20% even in non-hybrid applications. With the addition of a more robust energy storage and management system enabling full hybrid capabilities, NexxtDrive projects savings of up to 35%.
The two motors are assembled concentrically, which, combined with an extremely compact planetary gear set, allows the whole system to be engineered into a drivetrain with minimal impact on configuration. NexxtDrive says the DualDrive can be packaged in the same space as a conventional manual gearbox.
The DualDrive is based on an input split design (such as used in the Toyota and Ford hybrid powertrains), in which the single planetary gear set serves as the power split device. The system works without the need for clutches, torque converters or any form of mechanical gear change. In use, the majority of power is transferred through the mechanical path with very low losses, while a small fraction (never more than 25%) is transferred electrically between the motor-generators.
(A compound split approach, such as that being taken notably by GM/DaimlerChrysler/BMW, uses dual planetary gear sets, and dual disconnect clutches in addition to the dual motors.)
In plain CVT mode, controlling the relative speed of the two electric motors gives full control of the gearbox ratio, allowing the vehicle’s engine to operate at its most efficient speed in all conditions, delivering potential fuel and CO2 emissions savings of up to 20% even in a non-hybrid application, according to the company.
The electric motors can also replace the vehicle’s conventional starter motor and alternator to deliver stop-start functionality for further fuel savings in traffic along with a further reduction in total package cost.
Additional battery storage and energy management systems can provide support for a hybrid application, without altering the DualDrive gearbox in any way. In such applications, the company looks for CO2 reductions of up to 35%.
NexxtDrive has a completed detailed prototyping and simulation of the DualDrive system. In its portfolio of designs is a solution for rear-wheel drive passenger vehicles of up to 200 kW and extremely compact designs for front-wheel drive vehicles.
In studies currently underway for an unnamed OEM, NexxtDrive has demonstrated that the compact design of DualDrive can provide automatic transmission capabilities in vehicles where it has hitherto been impossible to package an automatic transmission to date. The system can also be scaled up for use in four-wheel drive, truck and bus applications.
DualDrive substantially reduces the risks for car makers looking at hybrid and CVT technology. With a similar unit cost to conventional automatic transmissions and straightforward integration into existing vehicle platforms, it will eliminate the daunting costs associated with development of vehicle-specific transmission solutions.—Rod Keech, Chairman of NexxtDrive
NexxtDrive is also working with Integral Powertrain on SuperGen2, a supercharger technology. (Earlier post.)
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