Patent ID: 8556768

Claim:
A planetary gear train of an automatic transmission for vehicles achieving multiple shift-speeds, the planetary gear train comprising: an input shaft adapted to receive engine torque; an output gear adapted to output a shifted torque; a first planetary gear set having a first sun gear, a first planet carrier, and a first ring gear; a second planetary gear set having a second sun gear, a second planet carrier, and a second ring gear; a compound planetary gear set formed by combining a third planetary gear set having a third sun gear, a third planet carrier, and a third ring gear, and a fourth planetary gear set having a fourth sun gear, a fourth planet carrier, and a fourth ring gear; a first rotational member consisting of the first sun gear and adapted to be directly connected to the input shaft; a second rotational member consisting of the first planet carrier and adapted to be directly connected to a transmission housing; a third rotational member consisting of the first ring gear and the second planet carrier; a fourth rotational member consisting of the second sun gear and the third sun gear; a fifth rotational member consisting of the second ring gear and adapted to be selectively connected to the transmission housing; a sixth rotational member consisting of the third planet carrier and the fourth ring gear, and adapted to be selectively connected to the input shaft or to the transmission housing; a seventh rotational member consisting of the third ring gear and the fourth planet carrier, and adapted to be directly connected to the output shaft; an eighth rotational member consisting of the fourth sun gear and adapted to be selectively connected to the input shaft; and six friction members consisting of clutches and brakes, the clutches being interposed between a selected rotational member among the rotational members and the input shaft or between selected rotational members, and the brakes being; interposed between a selected rotational member among the rotational members and the transmission housing.