Automatic transmission with a power train and the power train of a 4-speed automatic transmission for a vehicle

摘要

A powertrain which is used for a four-speed automatic transmission. The powertrain includes a first planetary gear unit and a second planetary gear unit. The first planetary gear unit is a first simple planetary gearset having first, second and third operating elements. The second planetary gear unit is a compound planetary gear unit including second and third simple planetary gearsets having fourth, fifth, sixth and seventh operating elements. The fourth operating element is fixedly connected to the first operating element, and the fifth operating element is variably connected to either the second operating element or the third operating element. Clutches are disposed between the fifth operating element and the second and third operating elements. Brake is interposed between at least one of the operating elements of the first and second planetary gear units to a transmission housing.