Bosch is demonstrating a new technology that they are developing for the electric vehicle market. The company is developing a continuously variable transmission for use in electric vehicles. While currently, many electric vehicles are single speed, or in some cases two speed, the continuously variable transmissions allow for essentially infinite speeds. This translates into an increase in efficiency for the electric vehicle and a reduction in the size of traction motor that is necessary while providing maximum torque applications at any wheel speed. Bosch cleverly dubbed its new technology CVT4EV. The transmission is based on current continuously variable transmission styles, with a push belt that connects two adjustable sheaves that change motor and wheel speed depending on load. Electric vehicles are notorious for providing massive acceleration and torque and amazingly, continuously variable transmissions promise even better acceleration while providing better efficiency, all out of smaller motor packages. Another benefit of using a continuously variable transmission would be the flexibility that it offers automakers, in that they could potentially use the same motor and chassis for multiple sized vehicles. From small cars to large trucks, all using the same motor size with different “gear” ratios for the continuously variable transmission, thereby reducing parts counts and complexities. Bosch’s performance testing has shown promising results thus far. During 150 KW testing of the transmission, the increase in acceleration from 0 to 100 km/h was shown to be approximately 3 percent, while acceleration at higher speeds was up to 13 percent higher. Meanwhile, the efficiency gain was approximately 4 percent overall, showing that overall benefits outweighed the complexity of the transmission and drivetrain. Towing capacity and road gradeability were two other factors that benefitted from the use of a continuously variable transmission. While electric vehicles are not currently known for their hauling capabilities, the use of a continuously variable transmission in an electric vehicle drivetrain shows promise to increasing the capability of the vehicle. The system is still in its development stages, however Bosch expects to release pricing of the components soon.
-taken from www.sae.org