Patent ID: 8235197

Claim:
A seal structure provided in an inner mechanism of an automatic shift gear comprising: a piston which is disposed in a housing to reciprocally move, forms a pressure chamber between the piston and the housing, and moves to press a clutch by supplying an operating oil to the pressure chamber; a canceller which is disposed opposite to the pressure chamber in the piston and forms a centrifugal canceller chamber between the canceller and the piston; a return spring which is disposed between the piston and the canceller and returns the piston; an opponent member which is disposed opposite to the centrifugal canceller chamber in the canceller and forms an oil path between the opponent member and the canceller; an outer circumferential seal unit which is provided on an outer circumferential portion of the canceller and comes into contact with the piston to seal an operating oil which is supplied to the centrifugal canceller chamber; and a second outer circumferential seal unit which is provided on the outer circumferential portion of the same canceller and comes into contact with the opponent member to seal an operating oil flowing through the oil path, wherein the second outer circumferential seal unit has an axial seal shape which comes into contact with an inner circumferential surface of a cylindrical shape provided on the opponent member.