Auto Electronics

DualDrive transmission promises fuel savings, low-cost hybrid capability

NexxtDrive is licensing DualDrive, a patent-protected transmission system designed to enable automakers to meet CO2 reduction requirements and integrate a hybrid electric capability quickly, at a relatively low cost.

DualDrive provides a cost-effective, efficient, continuously variable transmission solution, including an electric drive capability, in the same space as a conventional manual gearbox, according to Frank Moeller, director and chief engineer at NexxtDrive.

The system splits power transmission between an epicyclic mechanical gearbox and two electric motor/generators. It works without clutches, torque converters or any form of mechanical gear change. Most power is transferred through the gearbox, with the rest transferred electrically between the motor generators. Mechanically and electrically transmitted powers are recombined by the epicyclic gearbox and transmitted to the vehicle prop shaft.

“While electrical power transfer is less efficient than that transferred mechanically, the design of the epicyclic gearbox means that electric power transfer is minimized for the highest overall efficiency,” Moeller said.

Controlling the relative speed of the two electric machines 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%. Battery storage can be integrated into the system for full hybrid operation without altering the DualDrive gearbox. Moeller said the electric machines 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. In full hybrid applications, CO2 reductions will be at least 35% compared to conventional car designs.

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