BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a non-driving vehicle axle beam made in accordance with the present invention.
FIG. 2 is a top plan view of the vehicle axle beam.
FIG. 3 is a vertical cross-sectional view of the vehicle axle beam taken along the line III-III, FIG. 2.
FIG. 4 is a vertical cross-sectional view of the vehicle axle beam taken along the line IV-IV, FIG. 4.
FIG. 5 is a vertical cross-sectional view of the vehicle axle beam taken along the line V-V, FIG. 5.
FIG. 6 is a vertical cross-sectional view of another embodiment of the present invention, taken along an outboard side thereof.
FIG. 7 is a vertical cross-sectional view of the vehicle axle beam shown in FIG. 6, taken along an intermediate area of high stress during use.
FIG. 8 is a vertical cross-sectional view of the vehicle axle beam shown in FIGS. 6 and 7, taken along a medial portion thereof.
FIG. 9 is a flow chart illustrating various steps of the method embodying the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For purposes of description herein, the terms “upper”, “lower”, “right”, “left”, “rear”, “front”, “vertical”, “horizontal” and derivatives thereof shall relate to the invention as oriented in FIG. 1, and installed in an associated vehicle. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and process illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.
The reference numeral 1 (FIGS. 1-5) generally designates a non-driving vehicle axle beam embodying the present invention. Vehicle axle beam 1 comprises an elongate tube 3 constructed of hardenable steel which is formed to shape and selectively heat treated at the areas of high stress during use.
The illustrated vehicle axle beam 1 has a generally U-shaped plan configuration defined by a generally straight center portion 5, a pair of generally straight outer portions 6 and 7, and a pair of generally curved portions 8 and 9 interconnecting outer portions 6 and 7 with the opposite ends of center portion 5.
In one working embodiment of the present invention, as illustrated in FIGS. 1-5, the outer portions 6 and 7 of vehicle axle beam 1 have a generally square vertical cross-sectional shape (FIG. 3) defined by an integral top wall 11, a bottom wall 12 and sidewalls 13 and 14, which have a generally uniform wall thickness in the range of 2.5-3.5 millimeters, such as around 3.3 millimeters. As is apparent to those having ordinary skill in the art, the wall thickness of tube walls 11-14 will vary in accordance with the specific application.
The curved portions 8 and 9 of vehicle axle beam 1 are areas of high stress during use, and have a generally rectangular vertical cross-sectional shape, as shown in FIG. 4. In the example illustrated in FIG. 4, the walls 11-14 of the tube have been inelastically deformed so that sidewalls 13 and 14 are longer than the corresponding sidewalls of the outer portions 6 and 7, and the top and bottom walls 11 and 12 of curved portions 8 and 9 are somewhat shorter than the corresponding top and bottom walls of outer portions 6 and 7. The thickness of the walls 11-14 at the curved portions 8 and 9 is generally uniform, and in the illustrated example, has a thickness in the range of 5.0-6.0 millimeters, such as around 5.5 millimeters. As is apparent to those having ordinary skill in the art, the wall thickness of the tube walls 11-14 will vary in accordance with the specific application. It is noteworthy that, in the embodiment illustrated in FIGS. 1-5, the wall thickness of the curved portions 8 and 9 is greater than the wall thickness of the outer portions 6 and 7 and center portion 5, so as to provide greater strength and rigidity to vehicle axle beam 1 at the areas of high stress during use.
With reference to FIG. 5, the center portion 5 of the illustrated vehicle axle beam 1 has a generally rectangular shape. In the example shown in FIG. 5, the top and bottom walls 11 and 12 of center portion 5 are longer than the top and bottom walls of outer portions 6 and 7, and the sidewalls 13 and 14 of center portion 5 are somewhat shorter than the sidewalls 13 and 14 of outer portions 6 and 7. The walls 11-14 of center portion 5 have a generally uniform thickness in the range of around 2.5-3.5 millimeters, such as around 3.3 millimeters. As is apparent to those having ordinary skill in the art, the wall thickness of the tube walls 11-14 will vary in accordance with the specific application.
The vehicle axle beam 1 illustrated in FIGS. 1-5 may be manufactured in accordance with the following method. An elongate tube constructed of hardenable steel is selected, having a generally straight shape and a sidewall with a non-uniform thickness defining areas of increased thickness at the areas of high stress during use, as shown in FIGS. 4 and 7. In one working embodiment of the present invention, the selected elongate tube is constructed from a steel such as that known in the trade as BTR165 (DB200) and/or BAS100. The selected tube is cut to a predetermined length in accordance with the length and shape of the desired finished axle beam. The cut tube is positioned in a die having cooperating die sections that define a cavity with a shape which corresponds to the shape of the finished axle beam. Pressurized fluid is communicated with the interior of the cut tube mounted in the die, thereby inelastically deforming the cut tube under the force of the pressurized fluid into conformance with the shape of the die cavity. The cut tube is removed from the die to define a formed axle beam, which is in turn selectively heat treated at the areas of high stress during use to define the finished axle beam. The selective post form heat treatment of tube 3 may be accomplished with induction heating or the like, and serves to locally increase yield strength, which permits the use of thinner tubes for similar applications, so as to reduce material cost, and also improve vehicle dynamics, including ride and handling, by reducing unsprung mass.
In at least one embodiment of the present invention, the die cavity is shaped to alter the lateral cross-sectional shape of the cut tube, particularly at the areas of high stress during use to selectively work harden the sidewalls of the cut tube at these areas, as illustrated in FIGS. 3-8. It is to be understood that the vehicle axle beam 1 can be formed using various hydroforming techniques, as well as crush forming, and other related processes.
The reference numeral 1a (FIGS. 6-8) generally designates another embodiment of the present invention having a generally round vertical cross-sectional shape. Since vehicle axle beam 1a is similar to the previously describe vehicle axle beam 1, similar parts appearing in FIGS. 1-5 and 6-8, respectively, are represented by the same, corresponding reference numerals, except for the suffix “a” in the numerals of the latter. In the example illustrated in FIG. 6, the outer portion 6a of vehicle axle beam 1a has a generally circular vertical cross-sectional shape. The curved portion 8a of vehicle axle beam 1a has a generally ovate shape which is longer in the vertical direction, while the center portion 5a has a generally ovate shape which is longer in the horizontal direction.
As will be appreciated by those having ordinary skill in the art, the specific shape, size and thickness of the vehicle axle beam 1, 1a may be varied to accommodate a wide variety of different applications. Also, the degree and specific location of the heat treatment and increased wall thickness are preferably focused at the areas of high stress during use where they are most needed.
In the foregoing description, it will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims by their language expressly state otherwise.
Patent Application
20070283562
