Vehicle wheel disc, vehicle wheel including such a wheel disc and method for producing such a wheel disc and vehicle wheel

A steel wheel disc comprising:

• a hub located centrally within the wheel disc and defining a wheel axis, wherein the hub includes an axial hub hole and a plurality of lug bolt receiving holes formed therein such that the lug bolt receiving holes are spaced circumferentially about the hub hole equidistant from one another;
• an outer circumferential edge;
• and
• an annular transition portion radially extending between the hub and the outer circumferential edge, wherein the transition portion includes a plurality of vent hole regions circumferentially spaced around the transition portion about the wheel axis, and wherein at least one vent hole region includes a vent hole formed through the transition portion and defining an outer perimeter such that at least two bridging portions extend inwardly from the perimeter which subdivides the vent hole into at least three smaller holes formed through the transition portion at the at least one vent hole region, and wherein the transition portion is divided into first, second, third, fourth, and fifth sequential segments extending radially outwardly from the wheel axis, wherein the first segment is adjacent an outer edge of the hub and has a frustoconical shape sloped at a first angle relative to the wheel axis, and wherein the third segment has a frustoconical shape sloped at a second angle relative to the wheel axis which is different from the first angle, and wherein the second segment joins the first and third segments together with a curvature that smoothly blends in with the first and third segments, and wherein the fourth segment joins the third and fifth segments together with a curvature that smoothly blends in with the third and fifth segments, and wherein the fifth segment extends radially outwardly from the fourth segment to the outer circumferential edge of the wheel disc, and wherein the vent holes are formed only in the third segment.

A method of manufacturing a vehicle wheel disc including the steps of:

• (a) providing a metallic preform;
• (b) positioning the preform on a mandrel of a flow forming machine;
• and
• (c) flow forming the preform against the mandrel by a rolling tool to form a wheel disc having:
• a hub located centrally within the wheel disc and defining a wheel axis, wherein the hub includes an axial hub hole and a plurality of lug bolt receiving holes formed therein such that the lug bolt receiving holes are spaced circumferentially about the hub hole equidistant from one another;
• an outer circumferential edge having an outboard bead seat retaining flange;
• and
• an annular transition portion radially extending between the hub and the outer circumferential edge, wherein the transition portion includes a plurality of vent hole regions circumferentially spaced around the transition portion about the wheel axis, and wherein at least one vent hole region includes a vent hole formed through the transition portion and defining an outer perimeter such that at least two bridging portions extend inwardly from the perimeter which subdivides the vent hole into at least three smaller holes formed through the transition portion at the at least one vent hole region, wherein the transition portion is subdivided into a plurality of concentric segments.