BorgWarner Electrifies Transmissions
The complaints were piling up at Tesla Motors. Owners of its electric-powered Roadster were unhappy with the durability and performance of the car’s two-speed transmission system and the company’s leadership knew they needed to fix the problem fast. They turned to BorgWarner (www.bwauto.com
), who developed a single-speed electric drive transaxle capable of handling up to 400 Nm of torque with a top speed of up to 125 mph. The technology has now spawned an all-wheel drive (AWD) electric transaxle system that BorgWarner plans to put into production in 2010.
The systems are part of BorgWarner’s eGearDrive family of transaxles. The new 31-02 AWD unit weighs just 18 kg. It has a maximum input speed of 7,500 rpm and maximum torque input of 210 Nm. Using splash-lubrication, the transaxle provides front-wheel-drive operation with an electric secondary axle, similar to a through-the-road hybrid configuration. Appropriate reduction gear ratio controls manage the connection of the secondary axle during AWD operation. The secondary axle can also be used to provide boost, regenerative braking and AWD traction. An electronic disconnect feature allows the secondary transaxle to disconnect for increased efficiency at higher speeds. Engineers have also optimized the helical gear and bearing designs to improve torque capacity, accommodate high speed operating requirements while improving durability. BorgWarner claims the AWD eGearDrive system can improve fuel economy upwards of 15% when compared to base front-wheel drive systems.