Patent ID: 7384363

Claim:
A six-speed powertrain of an automatic transmission formed by combining a first simple planetary gear set including a first sun gear, a first ring gear, and a first planet carrier as operational elements thereof, a second simple planetary gear set including a second sun gear, a second ring gear, and a second planet carrier as operational elements thereof, and a third simple planetary gear set including a third sun gear, a third ring gear, and a third planet carrier as operational elements thereof, wherein the first sun gear is fixedly connected to a transmission case so as to always act as a fixed element, one of the first planet carrier and the first ring gear is fixedly connected to an input shaft so as to always act as an input element, the second sun gear is fixedly connected to the one of the first planet carrier and the first ring gear which is not fixedly connected to the input shaft, the second planet carrier and the third planet carrier are fixedly connected to each other, the third ring gear is variably connected to the second ring gear through a first clutch, the third sun gear is variably connected to the one which is not fixedly connected to the input shaft of the first planet carrier and the first ring gear through a second clutch, the third ring gear is variably connected to the input shaft through a third clutch so as to act as a variable input element, and is variably connected to the transmission case through a first brake and a one-way clutch disposed in parallel with each other, the third sun gear is variably connected to the transmission case through a second brake, and the third planet carrier acts as an output element.