Dissimilar material joining structure and producing method of dissimilar material joined body

1. A dissimilar material joining structure comprising:

a resin member having a plate shape, the resin member including a hole extending through the resin member;

a metallic member having a plate shape, the metallic member including a portion that faces the hole and an outer circumference of the hole; and

a metallic rivet including: a shaft disposed within the hole, the shaft having an axial direction extending in a plate thickness direction of the resin member; and a head integral with a first end in the axial direction of the shaft, the head disposed outside the hole,

wherein

the rivet is configured such that a brim portion of the head is in contact with a surface of the resin member, a second end in the axial direction of the shaft is joined to the metallic member via a weld, and the brim portion holds the resin member between the brim portion and the metallic member,

the shaft includes: a pillar extending from a center of the head; an enlarged diameter portion that is continuous with the pillar and having a diameter greater than a diameter of the pillar; and a punching portion joined to the metallic member via the weld,

the hole includes: a small-diameter hole portion that is adjacent to an outer circumference of the pillar, the small-diameter hole portion having an inner diameter equal to the diameter of the enlarged diameter portion; and a large-diameter hole portion that is adjacent to an outer circumference of the punching portion, the large-diameter hole portion having an inner diameter greater than the diameter of the enlarged diameter portion,

and

an entire outer circumference of the shaft is separated from an entire inner circumferential surface of the hole by a radially-extending gap.

2. The dissimilar material joining structure according to claim 1 , wherein

the resin member is a fiber-reinforced resin member, and includes:

a general portion; and

a projecting portion that projects from the general portion toward the metallic member, the projecting portion including: a portion where the large-diameter hole portion is formed; and a seat surface formed along an entire outer circumference of an aperture end in the large-diameter hole portion that faces the metallic member, the seat surface coming into surface contact with the metallic member,

and

the brim portion is configured to be overlaid with an entirety of the seat surface as viewed in the axial direction of the shaft.

3. A producing method of a dissimilar material joined body, the producing method joining a resin member having a plate shape to a metallic member having a plate shape by using a metallic rivet, the resin member including first and second oppositely-facing surfaces and a projecting portion projecting from the first surface and in which a recess is formed, the metallic rivet including a shaft extending in an axial direction and a head integral with a first end in the axial direction of the shaft, the head having a diameter greater than a diameter of the shaft, the shaft including (i) a pillar extending from a center of the head, (ii) an enlarged diameter portion that is continuous with the pillar and has a diameter greater than a diameter of the pillar and smaller than the diameter of the head, and (iii) a punching portion located at a second end in the axial direction of the shaft, the method comprising:

a first step of piercing a center of the recess provided in the projecting portion of the resin member, the recess having an inner diameter greater than the diameter of the enlarged diameter portion of the metallic rivet and smaller than the diameter of the head of the metallic rivet, the piercing being performed by pressing the punching portion into the resin member from the second surface of the resin member, so as to bring a brim portion of the head into contact with the second surface of the resin member; and

a second step of disposing the metallic member to face the first surface of the resin member and to contact the projecting portion after the first step and welding an end of the punching portion of the rivet to the metallic member while the resin member is held between the brim portion of the rivet and the metallic member.

4. The producing method according to claim 3 , wherein

in the second step, a pair of electrodes are disposed to hold a center of the head of the rivet, the shaft, and the metallic member between the electrodes, and

the pair of electrodes are supplied with current so as to weld the end of the punching portion of the rivet to the metallic member.