The eDifferential from the Schaeffler Group (www.schaeffler.us), with North American Automotive Technical Center in Troy, Michigan, combines an electric drive with a torque-vectoring transmission for cars and trucks. Torque vectoring lets the transmission send different levels and direction of torque to different wheels, which helps in cornering and handling, as well as safety. In this differential, wheels on the same axle can be getting torque values that differ by 1,475 ft-lb.
The device contains two water-cooled, permanent-magnet motors. An 11-hp motor regulates torque vectoring, while an 80-hp motor provides traction power. The differential is modular, so it will also work with larger or smaller traction motors.
The device uses a planetary-type reduction gearset, a compound planetary headset, and a spur-gear differential. The lightweight spur-gear differential eliminates up to 30% of weight compared with a bevel-gear differential, and it uses less than half the space. This translates to a weight savings of 6.5 lb and the transmission can be made 3.5-in. shorter.
The eDifferential can be installed on front or rear-wheel drive cars, or one can be installed on the front and one of the rear for four-wheel-drive vehicles.