Patent ID: 8210982

Claim:
A multi-step planetary transmission for an automobile, the transmission comprising: an input drive shaft ( 1 ) and an output shaft ( 2 ); first, second, third and fourth planetary gear sets (P 1 , P 2 , P 3 , P 4 ) being arranged in a housing (G) of the transmission, each of the first planetary gear set (P 1 ), the second planetary gear set (P 2 ), the third planetary gear set (P 3 ) and the fourth planetary gear set (P 4 ) having a sun gear, a planet carrier and a ring gear; at least third, fourth, fifth, sixth, seventh and eighth rotatable shafts ( 3 , 4 , 5 , 6 , 7 , 8 ); six shifting elements ( 03 , 04 , 05 , 15 , 17 , 18 ) comprising first, second and third brakes ( 03 , 05 , 04 ) and first, second, and third clutches ( 17 , 18 , 15 ) and selective engagement of the six shifting elements ( 03 , 04 , 05 , 15 , 17 , 18 ) achieves different gear ratios, between the drive shaft ( 1 ) and the output shaft ( 2 ), such that nine forward gears and one reverse gear can be implemented; the sun gear of the fourth planetary gear set (P 4 ) is coupled to the third shaft ( 3 ), and the third shaft ( 3 ) is connectable, via the first brake ( 03 ), to the housing (G) of the transmission; the planet carrier of the fourth planetary gear set (P 4 ) is permanently coupled to the output shaft ( 2 ), and the output shaft ( 2 ) is permanently connected to the ring gear of the second planetary gear set (P 2 ); the ring gear of the fourth planetary gear set (P 4 ) is to the seventh shaft ( 7 ); the seventh shaft ( 7 ) is connected to the planetary carrier of the second planetary gear set (P 2 ) and is connectable, via the a first clutch ( 17 ), to the drive shaft ( 1 ); the drive shaft ( 1 ) is connectable, via the second clutch ( 18 ), to the eighth shaft ( 8 ), and, via the third clutch ( 15 ), to the fifth shaft ( 5 ); the eight shaft ( 8 ) is coupled to the ring gear of the first planetary gear set (P 1 ); the fifth shaft ( 5 ) is permanently connected to both the sun gear of the first planetary gear set (P 1 ) and the sun gear of the third planetary gear set (P 3 ) and is connectable, via the second brake ( 05 ), with the housing (G) of the transmission; the planetary carrier of the first planetary gear set (P 1 ) is coupled to the sixth shaft ( 6 ), and the sixth shaft ( 6 ) is coupled to an element which is coupled to both the ring gear of the third planetary gear set (P 3 ) and the sun gear of the second planetary gear set (P 2 ); and the planetary carrier of the third planetary gear set (P 3 ) is coupled to the fourth shaft ( 4 ), and the fourth shaft ( 4 ) is connectable, via the third brake ( 04 ), with the housing (G) of the transmission.