Fastening structure including a bolt having a serration that is press-fit into a bolthole of a flange
A fastening structure capable of preventing deterioration in the flatness of a surface of a flange portion ( 2 ) when a serration ( 7 ) of a bolt ( 5 ) is press-fit into the flange portion ( 2 ). In this fastening structure, one portion in an axial direction of an outer peripheral surface ( 6 ) of the bolt ( 5 ) is provided with the serration ( 7 ). The bolt ( 5 ) is press-fit into a bolthole ( 3 ) formed through the flange portion ( 2 ) of a mounting member ( 1 ). The serration ( 7 ) is located apart from respective end surfaces ( 2 A) and ( 2 B) of the flange portion ( 2 ) by first and second distances (D, C), and the first and second distances (D, C) each exceed 13% of the thickness (A) of the flange portion ( 2 ). With this arrangement, the serration ( 7 ) presses a bolthole inner peripheral surface ( 13 ) only in the region located far apart from both of the end surfaces ( 2 A and 2 B) of the flange portion ( 2 ).
1. An automobile wheel bearing, comprising:
a bolt having a bolt head, a larger outer diameter portion extending in an axial direction of the bolt, and a smaller outer diameter portion extending in the axial direction of the bolt and provided with a thread portion;
an inner ring member having a flange portion in which a bolthole is formed and to which a brake disk is fixed by the bolt passing through the bolthole of the flange portion and a hole of the brake disk, an abutting surface of the bolt head abutting on a seat surface of the flange portion of the inner ring member;
an outer ring; and
a plurality of rolling elements disposed between the inner ring member and the outer ring,
wherein an outer peripheral surface of the larger outer diameter portion of the bolt is provided with an engaging portion engaging with the bolthole of the flange portion,
wherein a length of the engaging portion is shorter in an axial direction of the bolt than a thickness of the flange portion, and
wherein a center portion in the axial direction of the engaging portion coincides with a center portion in the axial direction of the flange portion.
2. The automobile wheel bearing as claimed in claim 1 , wherein a length in the axial direction of the engaging portion of the bolt does not exceed 74% of a thickness in the axial direction of the flange portion.