Patent ID: 8808134

Claim:
An automatic transmission comprising: an input shaft rotatably arranged relative to a transmission case and configured to be rotated with power of a driving source relative to the transmission case; an output member to output rotation of the input shaft using multiple gear-shifting; a first planetary gear system including a first sun gear, a first carrier, and a first ring gear; a second planetary gear system including a second sun gear, a second carrier, and a second ring gear; a third planetary gear system including a third sun gear, a third carrier, and a third ring gear; a fourth planetary gear system including a fourth sun gear, a fourth carrier, and a fourth ring gear; an engagement mechanism; four elements of either the second sun gear, the second carrier, the second ring gear, the third sun gear, the third carrier, or the third ring gear being defined as a first rotary element, a second rotary element, a third rotary element, and a fourth rotary element; the first sun gear, the first carrier, and the first ring gear being defined as a first element, a second element, and a third element; the fourth ring gear, the fourth carrier, and the fourth sun gear being defined as a fourth element, a fifth element, and a sixth element; the first element being connected to the input shaft; the fourth element being connected to the output member; the third element and the sixth element being connected to each other to provide a first connected body; the third rotary element and the fifth element being connected to each other to provide a second connected body; and the engagement mechanism comprising: a first clutch configured to releasably connect the first element to the second rotary element; a second clutch configured to releasably connect the first element to the first rotary element; a third clutch configured to releasably connect the second element to the fourth rotary element; a first brake configured to releasably connect the first connected body to the transmission case; a second brake configured to releasably connect the second rotary element to the transmission case; and a third brake configured to releasably connect the second element to the transmission case; and the multiple gear-shifting being provided by setting at least three of the first to third clutches and the first to third brakes in a connection state.