Coupling structure, coupling member having coupling structure, and method for manufacturing coupling member having coupling structure
A coupling structure includes a hollow rod section formed of a metal pipe and fastening sections formed by plastic deformation of the metal pipe so as to be connected with end sections of the hollow rod section. The fastening section includes a pair of base end sections which are each connected with a peripheral wall section forming a closed cross-section at the end section of the hollow rod section, and are separated from each other, and a bottom wall including a flat surface connected with the pair of the base end sections, and a pair of front end sections including a pair of side walls curving inwards from at least widthwise end sections of the bottom wall on a base end section side.
1. A coupling structure comprising:
a hollow rod section of a metal pipe; and
fastening sections connected with end sections of the hollow rod section,
wherein each of the fastening sections includes:
a pair of base end sections which are each connected with a peripheral wall section forming a closed cross-section at the end section of the hollow rod section, and are separated from each other, and
a pair of front end sections each including (i) a bottom wall including a flat surface connected to the pair of the base end sections, and (ii) a pair of side walls curving from at least widthwise end sections of the bottom wall on a base end section side of one front end section of the pair of front end sections, toward the other front end section of the pair of front end sections, and
a maximum width of each of the front end sections is greater than ½ of a length of an outer periphery in the end section of the hollow rod section.
2. The coupling structure according to claim 1 ,
wherein of the fastening sections is formed by plastically deforming a pair of wall sections formed by providing two slits extending in an axial direction of the metal pipe at the end sections of the metal pipe.
3. The coupling structure according to claim 1 ,
wherein, in the pair of the base end sections, mutual separation distance on a front end section side is greater than mutual separation distance on a hollow rod section side.
4. The coupling structure according to claim 1 ,
wherein the pair of the base end sections includes an outward reinforcing bead protruding outwards.
5. The coupling structure according to claim 1 ,
wherein the pair of the front end sections includes an inward reinforcing bead protruding inwards.
6. The coupling structure according to claim 1 ,
wherein the pair of the base end sections includes an outward reinforcing bead protruding outwards, and
the pair of the front end sections includes an inward reinforcing bead protruding inwards.
7. The coupling structure according to claim 1 ,
wherein a thick section of an uneven thickness metal pipe is applied to the fastening section.
8. The coupling structure according to claim 1 ,
wherein the metal pipe is a metal pipe having a tensile strength of 590 MPa or more.
9. The coupling structure according to claim 1 ,
wherein the metal pipe is a steel pipe.
10. A coupling member comprising the coupling structure according to claim 1 .