Automatic transmission

An automatic transmission equipped with a brake, comprising:

• a hub member joined to a transmission casing;
• a drum member joined to a given rotary member;
• a plurality of friction plates arranged between the hub member and the drum member;
• a piston for engaging the plurality of friction plates;
• a biasing member biasing the piston in an engagement direction;
• an engagement hydraulic pressure chamber to which hydraulic oil for biasing the piston in the engagement direction is supplied;
• and
• a disengagement hydraulic pressure chamber to which hydraulic oil for biasing the piston in a disengagement direction is supplied,
• wherein the biasing member, the engagement hydraulic pressure chamber, and the disengagement hydraulic pressure chamber are arranged radially inward of the plurality of friction plates at positions radially overlapping each other, and
• wherein the hub member comprises:
• a first hub member comprising a cylindrical portion having a splined region with which the friction plates are spline-engaged, wherein the first hub member is spline-engaged with the transmission casing;
• and
• a second hub member disposed on one side in an axial direction with respect to the first hub member, and formed with a part of a lubrication oil supply passage for supplying lubrication hydraulic oil to the friction plates, wherein the second hub member is fittingly engaged with the transmission casing such that it is connected to a valve body disposed beneath the transmission casing.