Seal structure and manufacturing method thereof

A manufacturing method of a seal structure that includes:

• an annular seal member of ring shape having an outer periphery and an inner periphery;
• a shaft member having a seal groove having a groove-bottom forming part at which the inner periphery of the annular seal member is disposed, an outer diameter of the groove-bottom forming part configured to increase along an axial direction of the annular seal member;
• and an inner peripheral wall member having an internal space encircled by an inner peripheral wall of the inner peripheral wall member, and arranging in the internal space the shaft member in which the annular seal member is disposed in the seal groove,
• wherein the annular seal member is formed of a plurality of ring-shaped parts overlapping with each other in the axial direction of the annular seal member, which are closed or unclosed when viewed in a radial direction orthogonal to the axial direction,
• wherein the shaft member includes a first main body and a second main body,
• wherein the first main body has a first joint at one end face thereof,
• wherein the second main body has a second joint which joins to the first joint of the first main body, the groove-bottom forming part of conical shape which connects to the second joint, and a flange part which is connected to the groove-bottom forming part and spreads out in the radial direction so as to be wider than the outer diameter of the groove-bottom forming part, and
• the method comprising:
• forming the seal groove with the one end face of the first main body, the groove-bottom forming part of the second main body and the flange part of the second main body by way of joining the first joint of the first main body and the second joint of the second main body, and fitting the annular seal member, in which an inner circumferential diameter of the inner periphery is substantially uniform along the axial direction, over the groove-bottom forming part from an exterior of the second joint;
• whereby an entirety of the inner periphery of the annular seal member is made to abut the groove-bottom forming part, the outer diameter of which increases along the axial direction of the annual seal member, along with the inner circumferential diameter of the inner periphery being made to increase following an increase in the outer diameter of the groove-bottom forming part, as well as increasing an outer circumferential diameter of the outer periphery;
• and
• whereby a first part of the outer periphery of the annular seal member having a first outer circumferential diameter is not made to abut the inner peripheral wall of the inner-peripheral wall member, and a second part of the outer periphery of the annular seal member having a second outer circumferential diameter is made to abut the inner peripheral wall of the inner-peripheral wall member, the first outer circumferential diameter being smaller than the second outer circumferential diameter, such that a contact state close to line contact is established between the outer periphery of the annular seal member and the inner peripheral wall of the inner peripheral wall member.