US Patent 9890833 Planetary gear train for automatic transmission of vehicles

A planetary gear train of an automatic transmission for a vehicle may include an input shaft, an output shaft, first to fourth planetary gear sets and seven friction elements disposed to selectively connect the rotation elements with the rotation element and selectively connect the rotation elements with a transmission housing, and wherein the input shaft is continuously connected to the second rotation element, the output shaft is continuously connected to the eleventh rotation element, the first rotation element is continuously connected to the sixth rotation element, the first rotation element is continuously connected to the eighth rotation element, the third rotation element is continuously connected to the seventh rotation element, the ninth rotation element is continuously connected to the tenth rotation element, and the output shaft is selectively connected with the third rotation element, and wherein three friction elements among seven friction elements are operated at each speed stage.