Clip attachment structure

A clip attachment structure in which a clip having a bead portion and a columnar leg portion protruding downward therefrom is attached such that the leg portion is inserted into a cylindrical insertion hole of a vehicular attachment-target member, which is an injection-molded product of resin, wherein

• the clip which is an injection-molded product of resin, has a plurality of plate-shaped engagement protrusions arranged in an insertion direction side into the insertion hole, the plate-shaped engagement protrusions extending outward from an outer circumferential surface of the leg portion in a non-elastically-deformed state,
• the engagement protrusions have sharpened corners at outermost edge portions corresponding to most distant positions from an axis of the leg portion on upper surfaces or lower surfaces thereof, the sharpened corners being sharpened to have a corner radius less than 0.2 mm, and
• the sharpened corners include engagement corners configured to, at a time of insertion into the insertion hole, slide on an inner circumferential wall surface of the insertion hole while the engagement protrusions are elastically deformed, and after the insertion, form an engaged state of digging into the inner circumferential wall surface by elastic restoration of the engagement protrusions within the insertion hole, thus preventing the clip from coming off from the insertion hole, and
• when the engaging protrusions are in the non-elastically-deformed state, the engagement corners are arranged so as to be slightly outside a periphery of the insertion hole, so that the engagement corners are configured to interfere and engage with the inner circumferential wall surface of the insertion hole with slight interference, and
• when the clip is attached to the insertion hole, all of the engagement protrusions are configured to be located in the insertion hole, and all of the engagement corners are configured to form an engaged state of digging into the inner circumferential wall surface within the insertion bole by elastic restoration of the engaging protrusions within the insertion hole, and
• each engagement protrusion has the upper surface, the lower surface, and a side surface connecting them,
• the engagement corners are lower edges of corner surfaces on both sides in the circumferential direction about the axis of a distal-end surface, which is a part of the side surface and is located at most distant position from the axis of the leg portion in each engagement protrusion,
• the clip has a plurality of reinforcement plate portions,
• all of the reinforcement plate portions have plate shapes extending in a length direction of the leg portion and protruding outward so that distances to distal-end surfaces located at most distant positions from the axis at a plurality of positions in the circumferential surface of the leg portion are approximately the same, and are provided integrally with the leg portion,
• each engagement protrusion is formed over an area between the reinforcement plate portions adjacent to each other in the circumferential direction so that each distance from the axis to each engagement corner is greater than each distance from the axis to the distal-end surface of each reinforcement plate, and when the clip is attached to the insertion hole, all of the engagement corners are configured to be allowed to form an engaged state of digging into the inner circumferential wall surface within the insertion hole by elastic restoration of the engaging protrusions within the insertion hole, and
• each engagement protrusion has a cutout formed therein that does not appear in a cross-section including a first engagement corner, which is one of the engagement corners at the both sides, and the axis of the leg portion, but appears to penetrate the engagement protrusion from top to bottom in a cross-section including a second engagement corner, which is the other of the engagement corners at the both sides, and the axis of the leg portion,
• each cutout is formed by removing an outer side of each engagement protrusion on a side facing the reinforcement plate portion so that a connection area between the engagement protrusion and the reinforcement plate portion adjacent to the second engaging corner portion is reduced, and
• in each engagement protrusion, an angle between the distal-end surface and the lower surface is less than 90° when viewed in the cross-section including the first engagement corner and the axis of the leg portion.