Patent ID: 8512198

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 engaged 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 single-pinion carrier which supports a second pinion gear engaged with the second sun gear and the second ring gear; an input shaft constantly coupled to the first sun gear; an output shaft constantly coupled to the second pinion carrier; a first rotary member constantly connecting the first ring gear and the second sun gear; a first friction element selectively connecting the first sun gear and the second ring gear; a second friction element selectively connecting the first pinion carrier and the second ring gear; a third friction element selectively interrupting a rotation of the first pinion carrier; and a fourth friction element selectively interrupting a rotation of the first rotary member, the automatic transmission attaining first to fourth forward speeds and one reverse speed.