Patent ID: 7442142

Claim:
An automatic transmission comprising: a first brake including first clutch plates, and selectively fixing a first rotating element of a planetary gear; a pump cover covering an oil pump, and defining a first receiving chamber receiving a torque converter, and a second receiving chamber receiving the planetary gear; a first cylindrical portion extending axially from the pump cover in the second receiving chamber, and including splines formed in an inner circumference of the first cylindrical portion, and arranged to support the first clutch plates of the first brake; a second cylindrical portion extending axially from the pump cover in the second receiving chamber, and being located radially inside the first cylindrical portion; a first cylinder chamber formed radially inside the first cylindrical portion, and arranged to generate a pressure for the first brake; a first piston including a first radially extending portion defining the first cylinder chamber with an outer circumference of the second cylindrical portion, and a second radially extending portion arranged to extend in a radial direction, and located radially outside the first cylinder chamber, the first piston being arranged to push the first clutch plates, by using the second radially extending portion, radially inside the first cylindrical portion; a lubricating oil supply hole located at a radial position which is between the first cylinder chamber and the first cylindrical portion, and which is separated from the first cylinder chamber in the radial direction, and arranged to supply the lubricating oil from the pump cover to the second receiving chamber in the axial direction; and a connection groove connecting the lubricating oil supply hole and the splines of the first cylindrical portion.