Patent ID: 8430786

Claim:
An automatic transmission comprising: a first planetary gearset including a first sun gear, a first ring gear, and a first pinion carrier as a single-pinion carrier which supports a first pinion gear, the first pinion gear meshing with the first sun gear and the first ring gear; a second planetary gearset including a second sun gear, a second ring gear, and a second pinion carrier as a double-pinion carrier which supports second pinion gears, one of the second pinion gears meshing with the second sun gear, the other of the second pinion gears meshing with the second ring gear, a third planetary gearset including a third sun gear, a third ring gear, and a third pinion carrier as a single-pinion carrier which supports a third pinion gear, the third pinion gear meshing with the third sun gear and the third ring gear; an input shaft; an output shaft; and six friction elements, wherein the automatic transmission is capable of shifting a gear stage to at least eight forward speeds by appropriately engaging and disengaging the six friction elements to thereby output a torque from the input shaft to the output shaft, wherein the input shaft is always connected to the first sun gear, wherein the output shaft is always connected to the first pinion carrier, wherein the third sun gear is always kept in a fixed state relative to a transmission case of the automatic transmission to constitute a first fixing member, wherein the first ring gear and the second sun gear are always connected to each other to constitute a first rotary member, wherein the second ring gear and the third ring gear are always connected to each other to constitute a second rotary member, wherein the six friction elements comprise a first friction element which selectively connects the second pinion carrier and the third pinion carrier, a second friction element which selectively connects the third pinion carrier and the first rotary member, a third friction element which selectively connects the first sun gear and the second pinion carrier, a fourth friction element which selectively connects the first pinion carrier and the second pinion carrier, a fifth friction element which selectively connects the first sun gear and the second rotary member, and a sixth friction element capable of interrupting rotation of the second rotary member, and wherein the at least eight forward speeds and one reverse speed are respectively established by simultaneous engagement of two friction elements selected from the six friction elements.