Patent ID: 8597152

Claim:
A planetary gear train of an automatic transmission for vehicles, comprising: an input shaft adapted to receive engine torque; an output gear adapted to output a shifted torque; a first compound planetary gear set having four rotation elements by combining first and second planetary gear sets and adapted to primarily shift torque input through two input paths into five speed ratios and to output the primarily shifted torque; a second compound planetary gear set having four rotation elements by combining third and fourth planetary gear sets and adapted to secondarily shift the torque input from the first compound planetary gear set and the torque input from the input shaft through one path into nine forward speeds and one reverse speed and to output nine forward speeds and one reverse speed; eight rotation shafts including two rotation elements connected to each other; and six friction members including three clutches coupled to the input shaft and adapted to selectively transmit the torque to selected ones of the rotational shafts, and including three brakes interposed between a selected rotational shaft among the rotational shafts and a transmission housing; wherein the second compound planetary gear set comprises: the third planetary gear set being a single pinion planetary gear set having a third sun gear, a third planet carrier, and a third ring gear; the fourth planetary gear set being a single pinion planetary gear set having a fourth sun gear, a fourth planet carrier, and a fourth ring gear; a fifth rotation shaft including the fourth sun gear and adapted to be directly connected to the second rotation shaft of the first compound planetary gear set; a sixth rotation shaft including the third ring gear and the fourth planet carrier, and adapted to be selectively connected to the input shaft; a seventh rotation shaft including the third planet carrier and the fourth ring gear, and adapted to be directly connected to the output gear; an eighth rotation shaft including the third sun gear and adapted to be selectively connected to the transmission housing; a third clutch interposed between the input shaft and the sixth rotation shaft; and a third brake interposed between the eighth rotation shaft and the transmission housing.