Patent ID: 7891476

Claim:
An automatic transmission, comprising: an input shaft; a transmission gear mechanism; and first and second multi-plate clutches operative to connect or disconnect the input shaft with first and second rotational elements respectively that form the transmission gear mechanism, wherein each of the first and second multi-plate clutches comprises a clutch outer cylinder portion that is provided to be coaxial with the input shaft and connected with the first rotational element or the second rotational element, a clutch inner cylinder portion that is provided to be coaxial with the input shaft, plural clutch plates that are provided between the clutch outer cylinder portion and the clutch inner cylinder portion so as to slide in an axial direction of the input shaft within the clutch outer cylinder portion or the clutch inner cylinder portion, and a clutch piston that is provided so as to slide in the axial direction of the input shaft and press the clutch plates for connecting the clutch outer cylinder portion with the clutch inner cylinder portion, wherein the clutch outer cylinder portion and the clutch inner cylinder portion of each of said first and second multi-plate clutches are provided in the axial direction of the input shaft, and there is provided a support wall portion that is connected with the input shaft and supports the clutch inner cylinder portion of each of the first and second multi-plate clutches, wherein at a one side of said support wall portion is provided either one of said clutch pistons, and at the other side of the support wall portion is the other of the clutch pistons, the clutch pistons being provided such that connecting directions thereof are opposite to each other, wherein there is provided a retaining portion that is supported at said support wall portion and provided between the plural clutch plates of the first multi-plate clutch and the plural clutch plates of the second multi-plate clutch, the retaining portion being operative to restrict movements of the respective plural clutch plates by pressing of the respective clutch pistons, and wherein said clutch inner cylinder portion includes a cutout portion and a non-cutout portion at one end thereof, the cutout portion and the non-cutout portion being formed at plural portions of a periphery of the one end of the clutch inner cylinder portion, the cutout portion being formed in a cutout shape so as to extend in the axial direction of the input shaft, said clutch piston includes a passing portion through which said non-cutout portion passes, and said one end of the clutch inner cylinder portion and the clutch piston are disposed so as to overlap with each other.