John F Roby

US Patent:

61830135, Feb 6, 2001

Filed:

Jul 26, 1999

Appl. No.:

9/359883

Inventors:

Steven K. Mackenzie - West Bloomfield MI
Ferdous M. Ghazi - Troy MI
John Roby - Northville MI

Assignee:

General Motors Corporation - Detroit MI

International Classification:

B62D 2100

US Classification:

280797

Abstract:

A vehicle frame has side rails which support the suspension system and body of the vehicle. The side rails have a rectangular cross-section with the end sections thereof having predetermined wall thicknesses and rectangular size, and a center section having a thinner wall thickness and a larger height dimension of the rectangular cross-section. A transition section connects respective end sections with the center section. The transition section has rectangular cross-sections and wall thickness at the respective junctures which matches the adjoining section. The frame side rail is manufactured by prebending a cylindrical tube of constant wall thickness into a shape consistent with the desired final shape; then hydroforming an intermediate work piece in a first die to provide wall thickness and perimeter characteristics commensurate with the final product; and then further hydroforming the intermediate work piece in a second die to provide the finished product or to provide two components which are joined to form the final frame side rail. When two intermediate work pieces are processed, each is formed with an end section and a part of the center section.