Joint unit and method for assembling joint unit

A method for assembling a joint unit, wherein the joint unit comprises

• a resin tube in which a liquid transferring channel extending along an axis is formed and whose cross section orthogonal to the axis is circular,
• a joint structure formed in a shaft shape along the axis, having an external thread in an outer circumferential face of the joint structure, and configured to be attached to an end of the resin tube, and
• a nut formed in a cylindrical shape along the axis and having an internal thread formed in an inner circumferential face of the nut, the internal thread being configured to be engaged with the external thread,
• wherein the joint structure comprises
• a main body,
• a guide part formed so as to protrude along the axis from the main body and configured to guide an outer circumferential face of the resin tube,
• a protrusion formed in a shaft shape so as to protrude along the axis from the main body and forming an insertion groove between the guide part and the protrusion, the resin tube being inserted in the insertion groove, and
• a fixing part formed so as to protrude along the axis from the main body and configured to fix the resin tube inserted in the insertion groove,
• wherein a coupling channel extending along the axis and configured to couple the liquid transferring channel and another channel is formed in the main body and the protrusion,
• wherein a tip of the protrusion is located closer to the main body than a tip of the guide part, and
• wherein the nut has a recessed part having an inner diameter that is larger than a first outer diameter of the guide part and smaller than a second outer diameter of the fixing part,
• the method comprising:
• an insertion step of guiding the outer circumferential face of the resin tube by the guide part and inserting the protrusion in the liquid transferring channel;
• and
• a fixing step of fastening the nut to the joint structure to cause the fixing part to come into contact with the recessed part and cause the tip of the fixing part to bite into the outer circumferential face of the resin tube.