US Patent 7128675 Dual path electrically-variable transmission

An electrically-variable transmission includes an input shaft, an output shaft, two electric motor/generators, and four nodes between which three parallel power paths are defined. Two of the power paths are mechanical and one of the power paths is electrical. The electric motor generators provide continuously variable speed ratios; manipulation of the power paths at the nodes provides a plurality of continuously variable operating modes for increased efficiency and smaller motor size. The transmission also provides an equal forward/reverse system with an input split.