| 摘要 |
A 7-speed power train of an automatic transmission is provided to improve a speed shifting feeling of the transmission by changing one of two activating elements during a speed shifting process. A double pinion planetary gear set(DPG) includes a first sun gear(S1), a first planetary carrier(PC1), a second planetary carrier(PC2), and a first ring gear(R1). The first sun gear is directly connected to a case. The first planetary carrier is gear-coupled with the first sun gear. The second planetary carrier is gear-coupled with the first sun gear and directly connected to an input shaft. The first ring gear is gear-coupled with the first and second planetary carriers. A Ravigneaux planetary gear set(RPG) includes a second sun gear(S2), a third planetary carrier(PC3), a fourth planetary carrier(PC4), a second ring gear(R2), and a third ring gear(R3). The second sun gear is connected to the first ring gear through a third clutch. The third planetary carrier is gear-coupled with the second sun gear and connected to the first ring gear through a fourth clutch. The fourth planetary carrier is gear-coupled with the second sun gear and connected to the case through a first brake. The fourth planetary carrier is connected to the input shaft through a first clutch. The second ring gear is gear-coupled with the third and fourth planetary carriers and connected to the case through a second brake. The second ring gear is connected to the first planetary carrier through a second clutch. The third ring gear is gear-coupled with the fourth planetary carrier and directly connected to an output shaft.
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