Vehicle wheel disc and manufacturing method of vehicle wheel disc

Abstract

A vehicle wheel disc includes a flat plate-shaped hub-mounted part, a cylindrical rim-mounted part, and a hat-shaped part. The hat-shaped part includes a hat top portion, a hat inner peripheral portion, and a hat outer peripheral portion. At a border between the hub-mounted part and the hat inner peripheral portion, a first connecting portion is provided, and at a border between the hat top portion and the hat outer peripheral portion, a second connecting portion is provided. The plate thickness of the hat outer peripheral portion is smaller than the plate thickness of an intermediate portion that is a portion from a border between the first connecting portion and the hat inner peripheral portion to a border between the hat top portion and the second connecting portion in the disc radial direction.

What is claimed is: 
     
         1 . A vehicle wheel disc comprising:
 a hub-mounted part having a shape of a flat plate extending in a disc radial direction that is to be mounted to a hub of a vehicle;   a rim-mounted part having a shape of a cylinder extending in a disc axial direction that is to be joined to a rim of a wheel; and   a hat-shaped part which connects the hub-mounted part and the rim-mounted part to each other in the disc radial direction and of which an entire region in a disc circumferential direction protrudes outward in the disc axial direction,   wherein the hat-shaped part includes:
 a hat top portion including only a curved portion that is curved in such a direction as to protrude outward in the disc axial direction as seen in a sectional view in the disc radial direction; 
 a hat inner peripheral portion that connects the hub-mounted part and the hat top portion to each other in the disc radial direction, and slopes outward in the disc axial direction while extending outward in the disc radial direction as seen in a sectional view in the disc radial direction; and 
 a hat outer peripheral portion that connects the hat top portion and the rim-mounted part to each other in the disc radial direction, and slopes inward in the disc axial direction while extending outward in the disc radial direction as seen in a sectional view in the disc radial direction, 
   wherein, at a border between the hub-mounted part and the hat inner peripheral portion, a first connecting portion is provided that has a curved shape curved in such a direction as to be depressed inward in the disc axial direction as seen in a sectional view in the disc radial direction,   wherein, at a border between the hat top portion and the hat outer peripheral portion, a second connecting portion is provided that has a curved shape curved in such a direction as to be depressed inward in the disc axial direction as seen in a sectional view in the disc radial direction, and   wherein a plate thickness of the hat outer peripheral portion is smaller than a plate thickness of an intermediate portion that is a portion from a border between the first connecting portion and the hat inner peripheral portion to a border between the hat top portion and the second connecting portion in the disc radial direction.   
     
     
         2 . The vehicle wheel disc according to  claim 1 , wherein an entire region of the hat outer peripheral portion in the disc radial direction extends straight as seen in a sectional view in the disc radial direction. 
     
     
         3 . The vehicle wheel disc according to  claim 2 , wherein the plate thickness of the hat outer peripheral portion is substantially constant throughout the entire region of the hat outer peripheral portion, and the plate thickness of the intermediate portion is substantially constant throughout an entire region of the intermediate portion. 
     
     
         4 . The vehicle wheel disc according to  claim 3 , wherein a ratio of the plate thickness of the hat outer peripheral portion to the plate thickness of the intermediate portion is 75% or lower. 
     
     
         5 . The vehicle wheel disc according to  claim 3 , wherein a maximum value of the plate thickness of the hat outer peripheral portion is smaller than a minimum value of the plate thickness of the intermediate portion.