Automatic transmission

An automatic transmission which changes rotations of an input shaft into multiple gear speeds transmitted to an output member via a plurality of planetary gear mechanisms disposed in a transmission case, wherein

• the plurality of planetary gear mechanisms includes three planetary gear mechanisms of a first planetary gear mechanism to a third planetary gear mechanism,
• the third planetary gear mechanism is of a single-pinion planetary gear mechanism comprised of the sun gear, the ring gear, and the carrier pivotally supporting a pinion intermeshed with the sun gear and the ring gear in such a way that the pinion can rotate and revolve freely,
• three elements comprised of a sun gear, a carrier and a ring gear of the first planetary gear mechanism are set as a first element, a second element and a third element, respectively, in the order of distances relative to gear ratios in a velocity diagram,
• three elements comprised of a sun gear, a carrier and a ring gear of the second planetary gear mechanism are set as a fourth element, a fifth element and a sixth element, respectively, in the order of distances relative to gear ratios in the velocity diagram,
• three elements comprised of a sun gear, a carrier and a ring gear of the third planetary gear mechanism are set as a seventh element, an eighth element and a ninth element, respectively, in the order of distances relative to gear ratios in the velocity diagram,
• a parallel gear is disposed to be adjacent to the seventh element and intermeshed with the pinion of the third planetary gear mechanism,
• the first element is coupled with the input shaft,
• the parallel gear is coupled with the output member,
• the third element and the fifth element are coupled to form a first coupling body,
• the sixth element and the ninth element are coupled to form a second coupling body,
• a first engagement mechanism couples the input shaft with the eighth element releasably,
• a second engagement mechanism couples the second element with the seventh element releasably,
• a third engagement mechanism couples the second element with the second coupling body releasably,
• a fourth engagement mechanism fixes the first coupling body to the transmission case releasably,
• a fifth engagement mechanism fixes the fourth element to the transmission case releasably, and
• a sixth engagement mechanism fixes the eighth element to the transmission case releasably.