Patent ID: 7766341

Claim:
A seal structure comprising an annular seal holding part formed in a joining portion of flow passages in fluid members connected at open ends thereof, and a sealing member held in an elastically deformed state between the fluid members and fitted in the seal holding part to hermetically seal the flow passage joining portion, the seal holding part is formed to open inwardly into the flow passage and include a first retaining surface, a second retaining surface, and a circumferential retaining surface, and the sealing member comprises: a first surface in contact with the first retaining surface; a second surface in contact with the second retaining surface; an inner surface joining inner edges of the first surface and the second surface, the inner surface being formed with a taper to having a diameter becoming smaller from the first surface to the second surface when the sealing member is in an uninstalled state; ends of the first surface and the second surface on an inner surface side are located at ends of the first retaining surface and the second retaining surface on the flow passage side; and an outer surface joining outer edges of the first surface and the second surface, the inner surface forming a flow passage inner wall having a concave shape, and the outer surface is formed with an engagement portion sized and shaped that the engagement portion is tightly held in the seal holding part and protrudes outwardly and close to the first surface, the engagement portion being formed with slits at circumferentially regular intervals.