Patent ID: 8110077

Claim:
A sealing jig for sealing an inner peripheral surface of a cylinder in contact with the cylinder inner peripheral surface as a surface to be processed of a cylinder block at a time of introducing treatment liquid to the cylinder inner peripheral surface, the sealing jig comprising: a sealing member made of an expandable material and having a ring-buoy shape; a seal support member for supporting one side of the sealing member; and a seal base disposed so as to face the seal support member and adapted to support another side of the sealing member, wherein when the treatment liquid is introduced inward, the sealing member is expanded only in a radial direction under regulation of the seal support member and the seal base so as to come into contact with the cylinder inner peripheral surface. wherein the seal support member or the seal base is provided with a fluid flow path including a blowing-off hole for blowing off fluid, the blowing-off hole is closed by the sealing member when the sealing member is expanded in a radial direction and is opened when the sealing member is contracted, and a contacting condition of the sealing member with the cylinder inner peripheral surface is confirmed in accordance with a pressure in the fluid flow path.