Automatic transmission

摘要

A hub 64 and a drum 66 are respectively provided inside and outside a forward clutch 21 (multiple-disc clutch) of an automatic transmission 1 for a vehicle. A piston 68 for pushing the forward clutch 21 and a hydraulic servo 69 for controlling the piston 68 are provided inside the hub 64 . A plurality of notched portions 70, 71 are formed in the piston 68 and the hub 64 with the positions thereof displaced from each other in the peripheral direction so that the piston 68 and the hub 64 are overlapped with each other in the axial direction in such a fashion that parts of one of the piston 68 and the hub 64 where no notched portions are formed are inserted into the notched portions 70 or 71 of the other. Thus, overlap between the piston 68 and the hub 64 in the axial direction reduces the size of the automatic transmission 1 .