Frictional engagement device for an automatic transmission.

摘要

A frictional engagement device for an automatic transmission, by which an input shaft (1) and an output shaft (20) are engaged or disengaged by use of oil pressure. A casing (2) connected to an input shaft (1) and a first piston (3) disposed in the casing (2) define a first oil pressure chamber (6). The first piston (3) is rotationally movable by predetermined angle and is axially movable by predetermined distance relative to the casing (2). A second piston (4) disposed in the first piston (3) defines a second oil pressure chamber (13) with the first piston (3), and the second piston (4) is axially movable relative to the first piston (3). Separator plates (17a,b,c) axially slidably connected to the first piston (3) and clutch discs (22a,b,c) axially slidably connected to a hub (21) which is fixedly connected to the output shaft (20) are engaged by a displacement of the second piston (4) by supplying pressurized oil to the second oil pressure chamber (13) and/or to the first oil pressure chamber (6). The oil passages in the casing (2) and the first piston (3) connect to each other when one of them rotationally moves relative to the other after the first piston (3) is displaced with supplying pressurized oil to the first oil pressure chamber (6). The pressurized oil supplied to the first oil pressure chamber (6) is then discharged and the engagement is released.