Joining structure, pipe joint, and method for forming joining structure

A pipe joint that is joined to a pipe member;

• a first member in which a housing space for housing a pipe end of the pipe member is formed;
• and
• a cylindrical member interposed between an outer peripheral surface of the pipe end and a housing surface, the housing surface being an inner peripheral surface of the first member forming the housing space, and
• a pushing member that applies axial force to the cylindrical member, wherein
• on a cross section parallel to an axial direction of the cylindrical member, a plurality of annular protrusions is provided on an inner peripheral surface of the cylindrical member along the axial direction;
• the pipe joint is configured to generate radially inward force on the cylindrical member by an axial force applied by the pushing member;
• the first member is formed with a force concentrating portion that concentrates the radially inward force on a part of the outer peripheral surface of the cylindrical member when moving along the outer circumferential surface of the cylindrical member, and
• the force concentration portion crushes and deforms the cylindrical member at the location where the radially inward force is concentrated, and
• as the force concentration portion moves along the outer circumferential surface of the cylindrical member, the plurality of annular protrusions bite into the outer circumferential surface of the tube member one by one along the axial direction,
• the joining structure airtightly or liquid-tightly joining the outer peripheral surface of the pipe end and the inner peripheral surface of the cylindrical member, making the pipe member and the cylindrical member inseparable.