Power transmission unit for electric vehicle

摘要

A power transmission unit for an electric vehicle has a planetary-gear type speed reducer disposed between and connected to an electric motor and a driving wheel. The speed reducer has two planetary gear sets in which common pinions are engaged with a fixed first ring gear and a second ring gear acting as an output portion. The common pinions are supported to a common carrier acting as an input portion. The number of teeth of the second ring gear is set to be the same as the sum of a number of teeth of the first ring gear and a number of the common pinions, and the common pinions are located at equal distances. Therefore, the power transmission unit has a proper reduction gear ratio and a high-torque transmission characteristic which are required for an electric vehicle while the speed reducer is formed small in size.