Patent ID: 8597153

Claim:
An automatic transmission comprising: an input shaft rotatably arranged relative to a transmission case and configured to be rotated with a driving force of a drive source relative to the transmission case, rotation of the input shaft being changed into rotation at a plurality of rotational speeds through a plurality of gear ratios; an output member to output rotation of the input shaft; a first planetary gear set including a first sun gear, a first carrier, and a first ring gear; a second planetary gear set including a second sun gear, a second carrier, and a second ring gear; a third planetary gear set including a third sun gear, a third carrier, and a third ring gear; a fourth planetary gear set including a fourth sun gear, a fourth carrier, and a fourth ring gear; an engagement mechanism; the first sun gear being connected to the input shaft to rotate together with the input shaft; the fourth ring gear being connected to the output member to rotate together with the output member; the first carrier being connected to the fourth sun gear to rotate together with the fourth sun gear, the first carrier and the fourth sun gear being defined as a first connected member; the third ring gear being connected to the fourth carrier to rotate together with the fourth carrier, the third ring gear and the fourth carrier being defined as a second connected member; the engagement mechanism comprising: a first clutch configured to connect and disconnect the first sun gear to and from the second carrier and the third carrier; a second clutch configured to connect and disconnect the first sun gear to and from the second sun gear; a third clutch configured to connect and disconnect the first connected member to and from the second ring gear and the third sun gear; a first brake configured to connect and disconnect the first connected member to and from the transmission case; a second brake configured to connect and disconnect the second carrier and the third carrier to and from the transmission case; and a third brake configured to connect and disconnect the first ring gear to and from the transmission case; and each of the plurality of gear ratios being provided by setting at least three of the first to third clutches and the first to third brakes in a connection state.