Patent attributes
A planetary gear train of an automatic transmission is disclosed to improve power delivery and fuel efficiency by applying six control elements to four planetary gear sets to achieve forward nine speed stages and one reverse speed stage. The planetary gear train includes: an input shaft; an output shaft; first to fourth planetary gear sets each having three rotational elements; four clutches and two brakes as the six control elements; and first to ninth shafts. In particular, the first shaft connects first and eleventh rotational elements, and the input shaft; the second shaft is connected with a second rotational element and selectively connected with the first shaft, the third shaft connects third and fifth rotational elements, and the fourth shaft is connected with a fourth rotational element and fixed to a transmission housing. In addition, the sixth shaft is selectively connected with the second and fifth shafts, respectively.
