Patent ID: 7377874

Claim:
An automatic transmission, in which an input shaft and an output shaft are rotatably supported on a common axis, and a rotation of the input shaft is shifted to a plurality of speeds and transmitted to the output shaft by connecting and fixing a plurality of friction engagement elements, comprising: a transmission case rotatably supporting the input shaft and the output shaft; a drive member, to which an output rotation of an engine is transmitted, that is rotatably supported on the common axis on a front side of the transmission case; and a speed-increasing planetary gear that constantly accelerates and transmits the output rotation of the engine to the input shaft, and includes a first rotation element that is connectable with the drive member via a start clutch, a second rotation element that is directly connected to the input shaft, and a third rotation element that is fixed to a support member of the transmission case, wherein: a hydraulic servo portion of the start clutch is provided rearward of the speed-increasing planetary gear in the drive member, a cylinder of the hydraulic servo portion of the start clutch is formed by a back wall of the drive member, a hydraulic oil passage communicating with the cylinder of the hydraulic servo portion is provided between the drive member and the support member, a lubrication hole is provided in the input shaft for supplying lubrication oil to portions of the speed-increasing planetary gear and a centrifugal hydraulic pressure canceller of the hydraulic servo portion, and the drive member includes a front wall, a cylindrical portion and the back wall, with the front wall provided forward of the speed increasing planetary gear, the back wall provided rearward of the speed increasing planetary gear, and the front wall and the back wall connected by the cylindrical portion that has a diameter larger than the speed increasing planetary gear.