Planetary gear train of automatic transmission for vehicle

A planetary gear train of an automatic transmission for a vehicle, comprising:

• an input shaft receiving torque of an engine;
• an output shaft outputting changed torque;
• a first planetary gear set being a single pinion planetary gear set and including first, second, and third rotation elements;
• a second planetary gear set being a single pinion planetary gear set and including fourth, fifth, and sixth rotation elements;
• a third planetary gear set being a single pinion planetary gear set and including seventh, eighth, and ninth rotation elements;
• a fourth planetary gear set being a single pinion planetary gear set and including tenth, eleventh, and twelfth rotation elements;
• a first rotation shaft including the first rotation element and directly connected to a transmission housing;
• a second rotation shaft including the second rotation element and the fifth rotation element and selectively connected to the transmission housing;
• a third rotation shaft including the third rotation element and selectively connected to the input shaft;
• a fourth rotation shaft including the fourth rotation element and directly connected to the input shaft;
• a fifth rotation shaft including the sixth rotation element and the seventh rotation element and selectively connected to the transmission housing;
• a sixth rotation shaft including the eighth rotation element and the twelfth rotation element and selectively connected to the input shaft and the transmission housing;
• a seventh rotation shaft including the ninth rotation element and the eleventh rotation element and directly connected to the output shaft;
• an eighth rotation shaft including the tenth rotation element and selectively connected to the input shaft;
• a first clutch selectively connecting the input shaft and the third rotation shaft;
• a second clutch selectively connecting the input shaft and the sixth rotation shaft;
• a third clutch selectively connecting the input shaft and the eighth rotation shaft;
• a first brake selectively connecting the second rotation shaft and the transmission housing;
• a second brake selectively connecting the fifth rotation shaft and the transmission housing;
• and
• a third brake selectively connecting the sixth rotation shaft and the transmission housing.

A planetary gear train of an automatic transmission for a vehicle, comprising:

• an input shaft receiving torque of an engine;
• an output shaft outputting changed torque of the engine;
• a first planetary gear set that is a single pinion planetary gear set and includes a first sun gear, a first planet carrier, and a first ring gear;
• a second planetary gear set that is a single pinion planetary gear set and includes a second sun gear, a second planet carrier, and a second ring gear;
• a third planetary gear set that is a single pinion planetary gear set and includes a third sun gear, a third planet carrier, and a third ring gear;
• and
• a fourth planetary gear set that is a single pinion planetary gear set and includes a fourth sun gear, a fourth planet carrier, and a fourth ring gear,
• wherein the planetary gear train of the automatic transmission for the vehicle further comprises:
• a first rotation shaft including the first sun gear and directly connected to a transmission housing;
• a second rotation shaft including the first planet carrier and the second planet carrier and selectively connected to the transmission housing;
• a third rotation shaft including the first ring gear and selectively connected to the input shaft;
• a fourth rotation shaft including the second sun gear and directly connected to the input shaft;
• a fifth rotation shaft including the second ring gear and the third sun gear and selectively connected to the transmission housing;
• a sixth rotation shaft including the third planet carrier and the fourth ring gear and selectively connected to the input shaft and the transmission housing;
• a seventh rotation shaft including the third ring gear and the fourth planet carrier and directly connected to the output shaft;
• an eighth rotation shaft including the fourth sun gear and selectively connected to the input shaft;
• and
• six friction elements disposed between at least one rotation shaft of the first to eighth rotation shafts and another rotation shaft of the first to eighth rotation shafts or between at least one rotation shaft of the first to eighth rotation shafts and a transmission housing.