US Patent 10281010 Planetary gear train of automatic transmission for vehicles

A planetary gear train of an automatic transmission for a vehicle improves 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 first planetary gear sets each having three rotational element: four clutches and two brakes as the six control elements; and first to ninth shafts. In particular, the first shaft connects a first rotational element 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; the fourth shaft is connected with a fourth rotational element and fixed to a transmission housing; and the fourth shaft is connected with the fourth rotational element and fixed to the transmission housing.