HYDRAULIC SERVO DEVICE FOR AUTOMATIC TRANSMISSION

摘要

PROBLEM TO BE SOLVED: To certainly carry out a position determination of a piston and realize a change to a piston having a different outer-diameter. SOLUTION: In a hydraulic servo device of an automatic transmission which is provided with a piston 6 slidably provided in a cylinder chamber 15 and having a piston shaft 5; a first hydraulic chamber 17 provided at one end side of the piston 6 and moving the piston 6 toward a direction of releasing a band brake 4 by supplying an oil pressure; a second hydraulic chamber 18 moving the piston 6 toward a direction of connecting the band brake 4 by supplying the oil pressure; a piston retainer 8 disposed opposed to the piston 6 and sealing the second hydraulic chamber 18; and a snap ring 10 disposed between the piston 6 and the piston retainer 8 and carrying out a position determination of the piston 6, an annular member 12 is provided between the snap ring 10 and the piston 6.