Gasket and seal structure

A gasket attached into a groove provided to one of two members, which are fixed and mounted to each other, and compressed between the two members to thereby form seal surfaces, which respectively come in close contact with a groove bottom surface of the groove and a surface of the other member, to seal a clearance between the two members,

• wherein a plurality of lip portions, for forming the seal surfaces in conjunction with one surface of the groove bottom surface of the groove and the surface of the other member, are provided so that a recessed portion separate from the one surface is formed between the adjacent lip portions,
• when a compression direction is defined as a height direction and a direction in which both side surfaces of the groove are opposed is defined as a width direction, in a section along the height direction and the width direction of the gasket, an entire area, which forms a seal surface in conjunction with the other surface of the groove bottom surface of the groove and the surface of the other member having a recessed portion, a protruding portion, or a combination of them and which is opposed to the other surfaces, of a profile of the section is an arciform portion including a perfect-circular curved line protruding toward the other surface, before the gasket is compressed between the two members,
• a radius of curvature ra of the curved line forming the arciform portion and width d0 of the section satisfy 0.75≦ra/d0≦2.0, and
• a height h0 of the section and a width d0 of the section satisfy 0.8≦h0/d0≦2.0.