Land vehicles – Wheeled – Running gear
Utility Patent
1999-03-12
2001-01-02
English, Peter (Department: 3619)
Land vehicles
Wheeled
Running gear
C280S781000, C180S312000, C296S204000, C029S897200
Utility Patent
active
06168204
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to body and frame assemblies for vehicles. More specifically, this invention relates to an improved structure for a vehicular body and frame assembly including a pair of side rails, wherein one or both of the side rails has at least one integral support surface formed therein to facilitate the mounting of various components on the vehicle frame assembly.
Many land vehicles in common use, such as automobiles, vans, and trucks, include a body and frame assembly that is supported upon a plurality of groundengaging engaging wheels by a resilient suspension system. The structures of known body and frame assemblies can be divided into two general categories, namely, separate and unitized. In a typical separate body and frame assembly, the structural components of the body portion and the frame portion of the vehicle are separate and independent from one another. When assembled, the frame portion of the assembly is resiliently supported upon the vehicle wheels by the suspension system and serves as a platform upon which the body portion of the assembly and other components of the vehicle can be mounted. Separate body and frame assemblies of this general type are found in most older vehicles, but remain in common use today for many relatively large or specialized use modern vehicles, such as large vans, sport utility vehicles, and trucks. In a typical unitized body and frame assembly, the structural components of the body portion and the frame portion are combined into an integral unit which is resiliently supported upon the vehicle wheels by the suspension system. Unitized body and frame assemblies of this general type are found in many relatively small modem vehicles, such as automobiles and minivans.
One well known example of a separate type of vehicular body and frame assembly is commonly referred to as a ladder frame assembly. A ladder frame assembly includes a pair of longitudinally extending side rails that are joined together by a plurality of transversely extending cross members. The cross members connect the two side rails together and provide desirable lateral, vertical, and torsional stiffness to the ladder frame assembly. The cross members can also be used to provide support for various components of the vehicle. Depending upon the overall length of the vehicle and other factors, the side rails of a conventional ladder frame assembly may be formed either from a single, relatively long structural member or from a plurality of individual, relatively short structural members that are secured together. For example, in vehicles having a relatively short overall length, it is known to form each of the side rails from a single integral structural member that extends the entire length of the vehicle body and frame assembly. In vehicles having a relatively long overall length, it is known to form each of the side rails from two or more individual structural members that are secured together, such as by welding, to provide a unitary structural member that extends the entire length of the vehicle body and frame assembly.
Traditionally, the side rails of known vehicle body and frame assemblies have been formed exclusively from open channel structural members, i.e., structural members that have a non-continuous cross sectional shape (U-shaped or C-shaped channel members, for example). Thus, it is known to use a single integral open channel structural member to form a side rail that extends the entire length of the vehicle body and frame assembly, as described above. Additionally, it is known to secure a plurality of such open channel structural members together to form the individual sections of a unitary side rail for a vehicle body and frame assembly, as also described above. However, the use of open channel structural members to form the side rails and cross members for vehicle body and frame assemblies has been found to be undesirable for several reasons. First, it is relatively time consuming and expensive to bend multiple portions of the side rails to conform to a desired final shape, as is commonly necessary. Second, after such bending has been performed, a relatively large number of brackets or other mounting devices must usually be secured to each of the side rails to facilitate the attachment of the various components of the vehicle to the body and frame assembly. Third, in those instances where the side rails are formed from a plurality of individual sections, it has been found difficult to maintain dimensional stability throughout the length of the side rail when the individual side rail sections are secured together.
More recently, it has been proposed to form the side rails and the cross embers from closed channel structural members, i.e., structural members that have a continuous cross sectional shape (tubular or box-shaped channel members, for example). In vehicle body and frame assemblies of this type, it is known that the closed channel structural member may be deformed to a desired shape by hydroforming. Hydroforming is a well known process that uses pressurized fluid to deform a closed channel structural member into a desired shape. To accomplish this, the closed channel structural member is initially disposed between two die sections of a hydroforming apparatus that, when closed together, define a die cavity having a desired final shape. Thereafter, the closed channel structural member is filled with a pressurized fluid, typically a relatively incompressible liquid such as water. The pressure of the fluid is increased to a magnitude where the closed channel structural member is expanded or otherwise deformed outwardly into conformance with the die cavity. As a result, the closed channel structural member is deformed into the desired final shape.
Hydroforming has been found to be a desirable forming process because portions of a closed channel structural member can be quickly and easily deformed to have a complex cross sectional shape. Additionally, hydroforming can be used to form appropriately shaped surfaces on the side rails to facilitate the mounting of various components directly on the vehicle frame assembly, without the use (or with minimal use) of separate brackets or other mounting devices. However, in known hydroforming methods that form integral mounting surfaces in the side rails, not only is the cross sectional shape of the closed channel structural member changed during the hydroforming process, but the wall thickness thereof is decreased. This decrease in wall thickness is caused when the perimeter of the closed channel structural member is expanded during the hydroforming process. Such wall thickness variations are usually considered to be undesirable because they can result in weaknesses in certain portions of the formed closed channel structural member.
One solution to this problem is to increase the wall thickness of the entire closed channel structural member such that the most extreme reductions in the wall thickness thereof would not adversely affect the overall strength of the member for its intended use. However, such over-designing undesirably increases the overall weight and cost of the closed channel structural member and the resultant vehicle frame component. An alternative solution is to employ a process known as end feeding. End feeding involves applying a mechanical force against one or both end portions of the closed channel structural member simultaneously as the interior portion is expanded. As a result, some of the metallic material of the end portions flows into the interior portion being expanded, thus minimizing the reduction in the wall thickness thereof. End feeding has been found to function satisfactorily in many instances, but is somewhat limited in its ability to cause the metallic material of the end portions of the closed channel structural member to flow into the expanded interior portion. Thus, it would be desirable to provide an improved structure for a component for a vehicular body and frame assembly, such as a side rail, having integral support surfac
Dana Corporation
English Peter
MacMillan Sobanski & Todd LLC
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