Lightweight rail assembly for vehicle

Abstract

A rail assembly for a chassis frame of a vehicle, such as a heavy-duty truck, may include a pair of rails offset from each other. Each of the pair of rails may include a first rail member formed of a first material and a second rail member formed of a second material. The first rail member may be fixedly coupled to the second rail member to form an elongate load-bearing beam structure comprising different materials. A density of the first material may be less than a density of the second material. The elongate load-bearing beam structure may be configured such that a compressive load is applied to the first rail member within a central region of the elongate load-bearing beam structure in static conditions and a tensile load is applied to the second rail member within the central region of the elongate load-bearing beam structure in static conditions.

Description

LIGHTWEIGHT RAIL ASSEMBLY FOR VEHICLEBACKGROUNDTechnical Field

[0001] The present disclosure relates to a rail assembly for a chassis of a vehicle, specifically a composite frame for a chassis of a heavy-duty truck.Description of the Related Art

[0002] Figure 1 illustrates a prior construction of a rail assembly 100 for a vehicle, namely, a heavy-duty truck. The rail assembly 100 includes a pair of rails 102, each consisting of a single member. Commonly, such rails are formed of a common material of sufficient strength to withstand the compressive and tensile forces applied to such rails, such as steel of a particular grade. However, as fuel efficiency and alternative energies have become a primary concern of automotive manufacturers, Applicant believes there exists a particular need for a light-weight alternative to traditional rail assemblies, which can maintain comparable strength and vibration characteristics despite reduced weight.BRIEF SUMMARY

[0003] The present disclosure is generally directed to chassis frames including a composite rail for a vehicle, such as a heavy-duty truck. The chassis frames described herein may provide a lighter chassis frame while maintaining performance standards of prior art chassis frames, such as with respect to strength, stiffness and vibrational characteristics. Further, the chassis frames described herein may provide enhanced customization of chassis frames for variants of vehicle chassis having different sizes and configurations while maintaining suitable performance standards.

[0004] A rail assembly for a chassis frame of a tractor vehicle (e.g., heavy-duty truck) may be summarized as including a pair of rails offset from each other. Each of the pair of rails may include a first rail member formed of a first material and a second rail member formed of a second material. The first rail member may be fixedly coupled to the second rail member to form an elongate load-bearing beam structure comprising different materials including the first material and the second material. A density of the first material of the first rail member is less than a density of the second material of the second rail member. The elongate load-bearing beamstructure may be configured such that a compressive load is applied to the first rail member within a central region of the elongate load-bearing beam structure in static conditions and a tensile load is applied to the second rail member within the central region of the elongate loadbearing beam structure in the static conditions.

[0005] In some embodiments, the first rail member and the second rail member may be fixedly coupled together by at least one fastener extending through the first rail member and the second rail member. In some embodiments, the at least one fastener may extend in a lateral direction through the first rail member and the second rail member. In some embodiments, the at least one fastener may further extend through a base of a cross-bracing beam. The cross-bracing beam may extend between the pair of rails.

[0006] In some embodiments, at least a portion of the first rail member may be positioned above at least a forward portion of the second rail member.

[0007] In some embodiments, at least a portion of the first rail member may include a z- shaped cross-sectional profile.

[0008] In some embodiments, a top flange of the first rail member may extend in an outboard direction away from a side wall of the first rail member.

[0009] In some embodiments, a cross-sectional profile of the elongate load-bearing beam structure may vary over a longitudinal length thereof. The elongate load-bearing beam may include at least one region with a Z-shaped cross-sectional profile and at least one region with a C-shaped cross-sectional profile.

[0010] In some embodiments, a rear portion of the first rail member and a forward portion of the second rail member may abut side-to-side to collectively form a T-shaped cross- sectional beam profile in an upper central region of the elongate load-bearing beam structure.

[0011] In some embodiments, the first rail member may include a forward portion, a center portion, and a rear portion. The center portion may extend further upward in a vertical direction than the forward portion.

[0012] In some embodiments, an upper surface of the rear portion of the first rail member may be aligned vertically with an upper surface of a center portion of the second rail member.

[0013] In some embodiments, the central region of the elongate load-bearing beam structure may include a through-going aperture formed between a lower portion of a center portion of the first rail member and an upper portion of a center portion of the second rail member.

[0014] In some embodiments, the second rail member may include a forward portion, a center portion, and a rear portion. The center portion may extend further downward in a vertical direction than the forward portion and the rear portion. In some embodiments, the second rail member may include a bottom flange extending inboard from a side wall of at least the center portion of the second rail member.

[0015] In some embodiments, a beam height of the elongate load-bearing beam structure may vary over a longitudinal length of the elongate load-bearing beam structure, and may include a maximum height that is located in the central region between opposing ends of the elongate load-bearing beam structure.

[0016] In some embodiments, an upper surface of a forward region of the elongate loadbearing beam structure may be offset to be lower than an upper surface of the central region and an aft region of the elongate load-bearing beam structure.

[0017] In some embodiments, a side wall of the second rail member may be thinner than at least one of a bottom flange of the second rail member and a top flange of the second rail member.

[0018] In some embodiments, a side wall of the second rail member may include a planar inboard surface.

[0019] In some embodiments, an outboard surface at a center portion of the second rail member may mate with an inboard surface of a rear portion of the first rail member, and an inboard surface at a forward portion of the second rail member may mate with an outboard surface of the first rail member.

[0020] In some embodiments, the first rail member may be configured to abut each of opposing inboard and outboard surfaces of the second rail member.

[0021] In some embodiments, the first rail member may include a compressive load capacity of at least 120 ksi.

[0022] In some embodiments, the second rail member may include a tensile load capacity of at least 220 ksi.

[0023] In some embodiments, the second material of the second rail member may have a higher tensile strength than the first material of the first rail member.

[0024] In some embodiments, when subject to tensile stress, the second material of the second rail member is more resistant to cracking than the first material of the first rail member.

[0025] In some embodiments, the first material consists of aluminum.

[0026] In some embodiments, the second material consists of steel.

[0027] In some embodiments, the rail assembly may further include, for each rail, at least one reinforcement structure coupled to an inner side wall of the first rail member or an inner side wall of the second rail member. The at least one reinforcement structure may be configured to provide enhanced localized strength of the elongate load-bearing beam structure.

[0028] In some embodiments, at least one of the at least one reinforcement structure may be fixedly coupled to a suspension assembly of the chassis frame of the tractor vehicle.

[0029] In some embodiments, the rail assembly may further comprise at least one crossbracing beam fixedly coupled to and extending between the pair of rails, such that the at least one cross-bracing beam is positioned in a region associated with a fifth-wheel connection assembly of the chassis frame.

[0030] A chassis frame may include any of the above-described rail assemblies. The natural resonant frequency of the chassis frame may be between 19 Hz and 24 Hz.

[0031] A collection of rail assemblies may include any of the above-described rail assemblies. The collection of rail assemblies may include a first rail assembly, a second rail assembly, and a third rail assembly. Each rail assembly may have identical or essentially identical front regions, identical or essentially identical rear regions, and different overall lengths.

[0032] A rail for a chassis frame of a tractor vehicle may include a first rail member formed of a first material and a second rail member formed of a second material. The first rail member may be fixedly coupled to the second rail member to form an elongate load-bearing beam structure comprising different materials including the first material and the second material. A density of the first material of the first rail member may be less than a density of the second material of the second rail member. The elongate load-bearing beam structure may be configured such that a compressive load is applied to the first rail member within a central region of the elongate load-bearing beam structure in static conditions and a tensile load is applied to the second rail member within the central region of the elongate load-bearing beam structure in the static conditions. The rail may be one of a pair of opposing rails of a rail assembly for a chassis frame of a tractor vehicle.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0033] Figure 1 shows a perspective view of an exemplary prior art rail assembly.

[0034] Figure 2 shows a perspective view of a rail assembly according to an example embodiment of the present disclosure.

[0035] Figure 3 shows a perspective view of a pair of first rail members of the rail assembly of Figure 2.

[0036] Figure 4 shows a side plan view of a first rail member of the rail assembly of Figure 2.

[0037] Figure 5 shows a front plan view of the first rail member of Figure 4.

[0038] Figure 6 shows a top plan view of the rail assembly of Figure 2.

[0039] Figure 7 shows a perspective view of a pair of second rail members of the rail assembly of Figure 2.

[0040] Figure 8 shows a side plan view of a second rail member of the rail assembly of Figure 2.

[0041] Figure 9A shows a side plan view of the rail assembly of Figure 2.

[0042] Figure 9B shows a side plan view of a first shortened rail assembly according to another embodiment of the present disclosure.

[0043] Figure 9C shows a side plan view of a second shortened rail assembly according to another embodiment of the present disclosure.

[0044] Figure 10 shows a front cross-sectional view of the rail assembly of Figure 2 taken along line 10-10 of Figure 9A.

[0045] Figure 10A shows a detail view of the front cross-sectional view of the rail assembly of Figure 10.

[0046] Figure 11 shows a front cross-sectional view of the rail assembly of Figure 2 taken along line 11-11 of Figure 9A.

[0047] Figure 12 shows a front cross-sectional view of the rail assembly of Figure 2 taken along line 12-12 of Figure 9A.

[0048] Figure 13 shows a perspective view of a chassis frame including the rail assembly of Figure 2.DETAILED DESCRIPTION

[0049] In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known structures and manufacturing techniques associated with vehicle chassis may not be shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments.

[0050] Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”

[0051] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0052] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0053] Figure 1 shows a perspective view of an exemplary prior art rail assembly 100 of a vehicle, such as a heavy-duty truck. Figure 2 shows a perspective view of a rail assembly 200 as part of a chassis frame of a vehicle, such as a heavy-duty truck, according to an example embodiment of the present disclosure. Rail assemblies 100, 200 may both have comparable strengths and vibration characteristics despite differing structural characteristics and configurations. The rail assembly 200 according to the example embodiment of the present disclosure may, for example, weigh significantly less than the prior art rail assembly 100, such as hundreds of pounds less. As can be seen in a comparison of rail assemblies 100, 200, the rail assembly 200 according to the example embodiment of the present disclosure may include multiple members 204, 208 as part of each rail 202a, 202b of a pair of opposing rails 202, which may consist of or comprise different materials from one another, while the rail assembly 100 of the prior art includes only a single member of common material throughout each rail 102a, 102b of the pair of rails 102. The rail assembly 200 of the example embodiment of the present disclosure may assist in improving fuel efficiency, while maintaining strength of the rail assembly and vibration and harshness characteristics of the rail assembly 200. The rail assembly 200 according to the example embodiment of this disclosure may provide over 200 pounds of weight savings in each rail when compared to the prior art rail assembly 100. In some embodiments, the rail assembly 200 may provide between 150 and 250 pounds of weight savingsin each rail compared to the prior art rail assembly 100. Overall, the rail assembly 200 may weigh at least 20%, at least 30% or at least 40% less than comparable prior art rail assemblies of similar length and performance, such as the rail assembly 100 of Figure 1.

[0054] The rail assembly 200 may be used as part of a chassis frame of a vehicle such as a heavy-duty truck. The rail assembly 200 may be used for a tractor portion of a semi-truck or tractor trailer. Additionally, the rail assembly 200 may be included in a number of other vehicles, such as, for example, a pick-up truck.

[0055] With reference to Figure 2, the rail assembly 200 may comprise the pair of rails 202. The pair of rails 202 may be laterally offset from each other. It should be understood that each rail 202a, 202b of the pair of rails 202 may generally mirror each other. Each rail 202a, 202b of the pair of rails 202 may have different bolt hole patterns due to relevant accessories or components (e.g., fuel tank, battery) attached to either side of the rail assembly 200, but the composite structure and general form factor may be identical or nearly identical for the pair of rails 202. Therefore, only one rail 202a of the pair of rails 202 will be described herein. However, the teachings of the rail 202a will similarly apply to the remaining rail 202b of the pair of rails 202.

[0056] As shown in Figure 2, each rail 202a, 202b of the pair of rails 202 may include a first rail member 204 and a second rail member 208 fixedly coupled to each other. The first rail member 204 and the second rail member 208 form an elongate load-bearing beam structure 212.

[0057] The first rail member 204 and the second rail member 208 may be formed of different materials. In other words, the first rail member 204 may be formed of a first material and the second rail member 208 may be formed of a second material. The elongate load-bearing beam structure 212 may comprise different materials including the first material and the second material. When a chassis frame including the rail assembly 200 is fully assembled, the rail assembly 200 may be configured such that, when in static conditions, a compressive load is applied to the first rail member 204 in a central region 216 of the elongate load-bearing beam structure 212 and a tensile load is applied to the second rail member 208 in the central region 216 of the elongate load-bearing beam structure 212. Such a configuration enables the first and second materials to be selected based on, at least in part, respective compressive or tensile strengths and / or toughness. Focusing on the respective compressive or tensile strengths and / or toughness may enable lighter materials to be selected for certain components, areas or regions, which may ultimately lower a weight of the rail assembly 200 and host vehicle and improve fuel efficiency.

[0058] A density of the first material of the first rail member 204 may be less than a density of the second material of the second rail member 208. In other words, the first material of the first rail member 204 may be a lighter material than the second material of the second rail member 208. The second material of the second rail member 208 may have a higher tensile strength than the first material of the first rail member 204. When subject to tensile stress, the second material of the second rail member 208 may be more resistant to cracking or failure than the first material of the first rail member 204.

[0059] In some embodiments, the first material of the first rail member 204 may comprise or consist of aluminum and the second material of the second rail member 208 may comprise or consist of steel, including, in particular, high strength steel. Aluminum is less dense than steel, and aluminum is also more resistant to cracking failures when subjected to compressive forces as compared to tensile forces. A composite structure as described herein enables use of a material more resistant to tensile failures in areas where tensile forces are more often encountered (such as steel), while enabling use of a lighter-density and lower strength material (such as aluminum) elsewhere.

[0060] Although some embodiments are described herein in the context of a rail 202 including rail members 204, 208 consisting of steel and aluminum, it is appreciated that other materials having different properties may be used for the rail members 204, 208 disclosed herein. For example, in some embodiments, the first material may comprise or consist of cast iron or magnesium. In some embodiments, the second material may comprise or consist of titanium or brass. In some embodiments, one of the first and second materials may be a steel material and the other one of the first and second materials may be a non-steel material. In some embodiments, the first and second materials may be incompatible materials in the sense of weldability (i.e., they are not able to be welded together to include sufficient weld strength or weld quality for applications in a vehicle chassis). In some embodiments, the first and second materials may be compatible materials in the sense of weldability (i.e., they are able to be welded together to include sufficient weld strength or weld quality for applications in a vehicle chassis). In some embodiments, the first and second materials may be compatible materials in the sense of their ability to be brazed together (i.e., they are able to be brazed together to include sufficient braze strength or braze quality for applications in a vehicle chassis).

[0061] Further details of the first rail members 204 of each rail 202a, 202b are shown in Figure 3 isolated from other components. The first rail member 204 may include a forward portion 220, a center portion 224, and a rear portion 228. As shown best in Figure 4, the centerportion 224 of the first rail member 204 may extend further upward in a vertical direction DI than the forward portion 220 of the first rail member 204. The front plan view of the first rail member 204 in Figure 5 shows that at least a portion 232 of the first rail member 204 may include a z-shaped cross-sectional profile 236. In some embodiments, a top flange 238 of the z- shaped cross-sectional profile 236 of the first rail member 204 may extend in an outboard direction from a side wall 239 of the first rail member 204. The outboard extension of the top flange 238 may allow easier removal and installation of any components or parts which may be positioned between the pair of rails 202, such as an engine, during fabrication and / or maintenance of the vehicle, for example. Such improved access to space 206 between the pair of rails 202 can be seen in the perspective view of the rail assembly 200 of Figure 2 or in the top view of the rail assembly 200 of Figure 6.

[0062] Second rail members 208 of each rail 202a, 202b are shown in Figure 7 isolated from other components. The second rail member 208 may include a forward portion 240, a center portion 244, and a rear portion 248. As can be seen in the side plan view of the second rail member 208 in Figure 8, the center portion 244 of the second rail member 208 may extend further downward in the vertical direction DI than the forward portion 240 and the rear portion 248. Such further extension in the downward vertical direction DI in the center portion 244 of the second rail member 208 may increase stiffness of the rail assembly 200 by increasing an effective beam height in this region.

[0063] With reference to Figure 7, the second rail member 208 may include a bottom flange 252 extending inboard from a side wall 256 in at least the center portion 244 of the second rail member 208. The side wall 256 of the second rail member 208 may include a planar inboard surface 264 and a planar outboard surface 265.

[0064] The first rail member 204 and the second rail member 208 may be fixedly coupled together, as shown in Figure 9A. As shown in Figures 10, 10A, and 11, the first and second rail members 204, 208 may be fixedly coupled by at least one fastener 272 extending through the first rail member 204 and the second rail member 208. Figure 11 shows the at least one fastener 272 may extend in a lateral direction D2 through an aperture 276 of the first rail member 204 and an aperture 280 of the second rail member 208. Although only several fasteners 272 are shown, it is appreciated that more fasteners may be provided in one or more fastening arrays to bolt the first and second rail members 204, 208 together in a particularly rigid configuration. In some embodiments, the first and second rail members 204, 208 may be fixedly coupled together bywelding. In some embodiments, the first and second rail members 204, 208 may be fixedly coupled together by brazing.

[0065] With reference back to Figure 9A, when the first rail member 204 and the second rail member 208 are coupled to each other, at least a portion 284 of the first rail member 204 may be positioned above at least the forward portion 240 of the second rail member 208. A beam height Hl of the elongate load-bearing beam structure 212 (z.e., a total height of the elongate load-bearing beam structure 212) may vary over a longitudinal length LI of the elongate loadbearing beam structure 212. The beam height Hl of the elongate load-bearing beam structure 212 may include a maximum height H2 that is located in the central region 216 between opposing ends 288, 290 of the elongate load-bearing beam structure 212. An upper surface 292 of a forward region 296 of the elongate load-bearing beam structure 212 may be offset to be lower than an upper surface 300 of the central region 216 and an upper surface 304 of an aft region 308 of the elongate load-bearing beam structure 212.

[0066] With reference to Figure 11, an upper surface 312 of the rear portion 248 of the first rail member 204 may be aligned vertically with an upper surface 314 of the center portion 244 of the second rail member 208 to present a collective upper surface. The rear portion 228 of the first rail member 204 and a forward portion 240 of the second rail member 208 may abut side-to-side to collectively form a T-shaped cross-sectional beam profile 352 in an upper central region 356 of the elongate load-bearing beam structure 212.

[0067] With reference back to Figure 10A, the first rail member 204 may be configured to abut each of opposing inboard and outboard surfaces 264, 265 of the side wall 256 of the second rail member 208. As the inboard surface 264 of the side wall 256 may be planar, the first rail member 204 may be configured such that the first rail member 204 is bent or otherwise formed to mate to both the inside surface 264 and the outboard surface 265 of the second rail member 208. Specifically, the outboard surface 265 at the center portion 244 of the second rail member 208 may mate with the inboard surface 241 at the rear portion 228 of the first rail member 204. The inboard surface 264 at the forward portion 240 of the second rail member 208 may mate with an outboard surface 243 of the first rail member 204.

[0068] With reference back to Figure 9 A, the central region 216 of the elongate loadbearing beam structure 212 may include a through-going aperture 340 formed between a lower portion 344 of the center portion 224 of the first rail member 204 and an upper portion 348 of the center portion 244 of the second rail member 208. In other words, the through-going aperture 340 may be defined by a lower portion 344 of the first rail member 204 which is configured to beat least partially spaced apart from the upper portion 348 of the center portion 244 of the second rail member 208. The lower portion 344 of the of the center portion 224 may extend downward in a sloped fashion while approaching the rear portion 228 of the first rail member 204. The through-going aperture 340 may extend along at least a substantial portion (e.g., at least 10%, at least 20%, or at least 30%) of the longitudinal length LI of the elongate load-bearing beam structure 212. The through-going aperture 340 may extend along at least a substantial portion (e.g., at least 10%, at least 20%, or at least 30%) of the height Hl of the elongate load-bearing beam structure 212.

[0069] A cross-sectional profile of the elongate load-bearing beam structure 212 may vary over the longitudinal length LI thereof. For example, the elongate load-bearing beam 212 may include at least one region 213 with a Z-shaped cross-sectional profile 364, as defined by the first rail member 204 as shown in Figure 5, and at least one region 368 with a C-shaped cross-sectional profile 372. The C-shaped cross-sectional profile 372 can be seen in the perspective view of the second rail member of Figure 7 or the front cross-sectional view of the rail assembly 200 of Figure 12.

[0070] When the first rail member 204 and the second rail member 208 are coupled together, each of the first rail member 204 and the second rail member 208 may include a compressive load capacity and a tensile load capacity. For example, when the first rail member 204 and the second rail member 208 are coupled together in the configuration shown in Figures 2, 6, and 9-12, the first rail member 204 may include a compressive load capacity of at least 120 ksi. In some embodiments, when the first rail member 204 and the second rail member 208 are coupled together, the first rail member 204 may include a compressive load capacity of 110 ksi. In some embodiments, when the first rail member 204 and the second rail member 208 are coupled together, the first rail member 204 may include a compressive load capacity of 100 ksi. As a further example, when the first rail member 204 and the second rail member 208 are coupled together in the configuration shown in Figures 2, 6, and 9-12 the second rail member 208 may include a tensile load capacity of at least 220 ksi. In some embodiments, when the first rail member 204 and the second rail member 208 are coupled together, the second rail member 208 may include a compressive load capacity of 210 ksi. In some embodiments, when the first rail member 204 and the second rail member 208 are coupled together, the second rail member 208 may include a compressive load capacity of 200 ksi.

[0071] Is some instances, a material thickness may be varied and / or optimized in different areas to maintain strength while reducing or minimizing weight of the elongate load-bearing beam structure 212. For example, as shown in Figure 11, the side wall 256 of the second rail member 208 may be formed to be thinner than at least one of the bottom flange 252 of the second rail member 208 and a top flange 268 of the second rail member 208, in order to further minimize the weight of the second rail member 208 to be included in the rail assembly 200 without jeopardizing required strength and stiffness.

[0072] The longitudinal length LI of the elongate load-bearing beam structure 212 may vary to provide a desired length for a chassis among a plurality of chassis configurations. For example, the longitudinal length LI may be altered to enable the rail assembly 200 to satisfy a desired wheelbase of a vehicle. Figure 9B shows an exemplary first shortened rail assembly 200' and Figure 9C shows an exemplary second shortened rail assembly 200".

[0073] The longitudinal length LI may be varied by altering an overall length L2 (Figure 4) of the first rail member 204 and an overall length L3 (Figure 8) of the second rail member 208 and / or amount of overlap therebetween. The overall length L2 of the first rail member 204 may be varied by altering the center portion 224 of the first rail member 204. The overall length L3 of the second rail member 208 may be varied by altering the center portion 244 of the second rail member 208. Such alterations of the center portions 224, 244 of the rail members 204, 208 enables customization of the longitudinal length LI of the rail assembly 200, while reducing or minimizing excessive material which may be present on rail members 204, 208 and thereby reducing or minimizing a weight of the rail assembly 200. It also enables the various rail assemblies 200, 200' and 200" to maintain common sections to ease fabrication and assembly of host vehicles.

[0074] As an example, when comparing the rail assemblies 200, 200' of Figures 9 A and 9B, it can be seen that a central portion 224' of a first rail member 204' of the first shortened rail assembly 200' is shorter than the central portion of 224 of the first rail member 204 of the rail assembly 200. Similarly, when comparing the rail assemblies 200, 200' of Figures 9A and 9B, it can be seen that a central portion 244' of a second rail member 208' of the first shortened rail assembly 200' is shorter than the central portion of 244 of the second rail member 208 of the rail assembly 200. Such shortened central portions shorten an overall longitudinal length L4 of the first shortened rail assembly 200'.

[0075] In another example, when comparing the rail assemblies 200', 200" of Figures 9B and 9C, it can be seen that a central portion 224" of a first rail member 204" of the second shortened rail assembly 200" is shorter than the central portion of 224' of the first rail member 204' of the first shortened rail assembly 200'. Similarly, when comparing the rail assemblies 200',200" of Figures 9B and 9C, it can be seen that a central portion 244" of a second rail 208" of the second shortened rail assembly 200" is shorter than the central portion of 244' of the second rail member 208' of the first shortened rail assembly 200'. Such shortened central portions shorten an overall longitudinal length L5 of the second shortened rail assembly 200".

[0076] In some embodiments, the length of a central portion of rail members may not be adjusted, but instead, rail members may be repositioned relative to each other to alter the longitudinal length of the rail assembly by changing an overlap therebetween. In such embodiments, a forward rail member e.g., first rail member 204 in rail assembly 200) may be positioned further aft relative to an aft rail member (e.g., second rail member 208) when compared to the configuration shown in Figure 9A. Similarly, the aft rail member may be positioned further forward relative to the forward rail member when compared to the configured shown in Figure 9 A. Such positioning may be enabled by a plurality of bolt holes extending along a longitudinal length of a rail assembly, such as a plurality of bolt holes 273 extending along the longitudinal length LI of the rail assembly 200. Such plurality of bolt holes 273 enable the forward and aft rail members to be positioned in a plurality of positions relative to each other without altering the rail members 202 because the fasteners may extend through any of the plurality of bolt holes, thus, allowing easy customization of the longitudinal length LI of the rail assembly 200.

[0077] With reference now to Figure 11, the rail assembly 200 may further include at least one cross-bracing beam 376 extending between the pair of rails 202a, 202b. The at least one fastener 272 described above for coupling the rail members 204, 208 together may further extend through a base 380 of each of the at least one cross-bracing beam 376, coupling each of the at least one cross-bracing beam 376 to the pair of rails 202. More specifically, the at least one fastener 272 may couple each of the at least one cross-bracing beam 376 to at least one of the first rail member 204 and the second rail member 208. For example, the at least one fastener 272 may extend through an aperture 382 of the base 380 of the at least one cross-bracing beam 376, the aperture 280 of the second rail member 208, and the aperture 276 of the first rail member 204, as shown in Figure 11. The at least one fastener 272 may couple the base 380 of the at least one cross-bracing beam 376, the second rail member 208, and / or the first rail member 204 together. The at least one cross-bracing beam 220 may be coupled by such a configuration to each rail 202a, 202b of the pair of rails 202 with separate fasteners 272 coupling each of the at least cross-bracing beam 376 to each rail 202a, 202b of the pair of rails 202. In other instances,fasteners may be provided for coupling the cross-bracing beam 376 to the rails 202a, 202b which are separate and distinct from fasteners for coupling the rail members 204, 208 together.

[0078] With reference to Figures 2 and 13, the rail assembly 200 may further include at least one reinforcement structure 384. Each reinforcement structure of the at least one reinforcement structure 384 may be coupled to one of the rails 202a, 202b of the pair of rails 202. The at least one reinforcement structure 384 may be coupled to at least one of the inboard surface 241 of the side wall 239 of the first rail member 204 (z.e., the inner side wall 341 of the first rail member 204) or the inboard surface 264 of the side wall 256 of the second rail member 108 (z.e., the inner side wall 264 of the second rail member 208). The at least one reinforcement structure 384 may be configured to provide enhanced localized strength of the elongate loadbearing beam structure 212 such as by increasing an effective thickness of the beam in certain desired locations. Therefore, such at least one reinforcement structure 384 may be utilized in areas of the rail assembly 200 which are expected to encounter high stress during use of the vehicle including the rail assembly 200. Such areas may include, for example, areas adjacent to suspension assemblies, an engine, and or a cabin section.

[0079] With reference now to Figure 13, the rail assembly 200 may form part of a chassis frame 396, which forms a part of a tractor vehicle (partially shown). The chassis frame 396 may include a plurality of wheel assemblies 408 coupled to the rail assembly 200 by a suspension assembly 412. The chassis frame 396 may further include a fifth-wheel connection assembly 416, which may be coupled to the rail assembly 200.

[0080] At least one reinforcement structure 384 may be fixedly coupled to, or coupled to a rail 202a, 202b adjacent to, the suspension assembly 396 of the chassis frame 396 of the tractor vehicle 404. The suspension assembly 412 may transmit additional stress to the rail assembly 200. The coupling of the at least one reinforcement structure 384 to the suspension assembly 412, or in the vicinity of the suspension assembly 412, may strengthen portions of the rail assembly 200 subject to the additional stress transmitted by the suspension assembly 412 without unnecessarily increasing the thickness of the entirety of the rails 202. In this manner, selective areas may be reinforced to provide enhanced strength to optimize material distribution throughout the rail assembly 200.

[0081] With reference to Figures 12 and 13, the rail assembly 200 may include at least one fifth-wheel cross-bracing beam 424 fixedly coupled to and extending between each rail 202a, 202b of the pair of rails 202. The at least one fifth-wheel cross-bracing beam 424 may be positioned in a region 428 associated with the fifth-wheel connection assembly 416 of the chassisframe 396. For example, the at least one fifth-wheel cross-bracing beam 424 may be positioned below and coupled to the fifth-wheel connection assembly 416 such that the at least one fifthwheel cross-bracing beam 424 supports the fifth-wheel connection assembly 416. In some embodiments, the fifth-wheel connection assembly 416 may be directly coupled to the pair of rails 202, and in such embodiments, the at least one fifth-wheel cross-bracing beam 424 may be positioned between the points at which the fifth- wheel connection assembly 416 couples to the pair of rails 202.

[0082] In at least one advantageous embodiment, the chassis frame 396 utilizing the above-described rail assembly 200 may be designed to have a natural resonant frequency between 19 Hz and 24 Hz, between 20 Hz and 23 Hz, or between 21 Hz and 22 Hz in order to reduce or minimize vibrations in the chassis frame when subjected to vibrational stimulus associated with oft encountered driving conditions.

[0083] In view of the above, it is appreciated that embodiments disclosed herein may provide chassis frames having an overall lower weight relative to traditional chassis frames while maintaining performance standards, such as with respect to strength, stiffness and vibrational characteristics. This is advantageous in, among other things, reducing material costs and lowering vehicle weight, thereby leading to increased fuel efficiency. Other advantages and benefits will be appreciated by those of ordinary skill in the relevant art upon a detailed review of the disclosure.

[0084] Additional Considerations

[0085] The devices and systems of the disclosure each have several innovative aspects, no single one of which is solely responsible or required for the desirable attributes disclosed herein. The various features described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. Various modifications to the implementations described in this disclosure may be readily apparent to those of ordinary skill in the art, and the generic principles defined herein may be applied to other implementations. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein.

[0086] Certain features that may be described in this specification in the context of separate implementations also may be implemented in combination in a single implementation. Conversely, various features that may be described in the context of a single implementation also may be implemented in multiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. No single feature or group of features is necessary or indispensable to each and every embodiment.

[0087] Conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and / or steps. Thus, such conditional language is not generally intended to imply that features, elements and / or steps are in any way required for one or more embodiments. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. In addition, the articles “a,” “an,” and “the” as used in this application and the appended claims are to be construed to mean “one or more” or “at least one” unless specified otherwise.

[0088] Moreover, although aspects of the various implementations have been described in the context of heavy-duty trucks, such as long-haul tractors, it is appreciated that aspects of the implementations described herein, may be applicable to other applications, such as personal vehicles.

[0089] In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.

Claims

CLAIMS1. A rail assembly for a chassis frame of a tractor vehicle, the rail assembly comprising a pair of rails offset from each other, each of the pair of rails comprising: a first rail member formed of a first material; and a second rail member formed of a second material, the first rail member fixedly coupled to the second rail member to form an elongate load-bearing beam structure comprising different materials including the first material and the second material, wherein a density of the first material of the first rail member is less than a density of the second material of the second rail member, and wherein the elongate load-bearing beam structure is configured such that a compressive load is applied to the first rail member within a central region of the elongate load-bearing beam structure in static conditions and a tensile load is applied to the second rail member within the central region of the elongate load-bearing beam structure in the static conditions.

2. The rail assembly of claim 1, wherein the first rail member and the second rail member are fixedly coupled together by at least one fastener extending through the first rail member and the second rail member.

3. The rail assembly of claim 2, wherein the at least one fastener extends in a lateral direction through the first rail member and the second rail member.

4. The rail assembly of claim 2, wherein the at least one fastener further extends through a base of a cross-bracing beam, the cross-bracing beam extending between the pair of rails.

5. The rail assembly of claim 1, wherein at least a portion of the first rail member is positioned above at least a forward portion of the second rail member.

6. The rail assembly of claim 1, wherein at least a portion of the first rail member includes a z-shaped cross-sectional profile.

7. The rail assembly of claim 6, wherein a top flange of the first rail member extends in an outboard direction away from a side wall of the first rail member.

8. The rail assembly of claim 1, wherein a cross-sectional profile of the elongate load-bearing beam structure varies over a longitudinal length thereof, and the elongate loadbearing beam includes at least one region with a Z-shaped cross-sectional profile and at least one region with a C-shaped cross-sectional profile.

9. The rail assembly of claim 1, wherein a rear portion of the first rail member and a forward portion of the second rail member abut side-to-side to collectively form a T-shaped cross-sectional beam profile in an upper central region of the elongate load-bearing beam structure.

10. The rail assembly of claim 1, wherein the first rail member includes a forward portion, a center portion, and a rear portion, and wherein the center portion extends further upward in a vertical direction than the forward portion.

11. The rail assembly of claim 10, wherein an upper surface of the rear portion of the first rail member is aligned vertically with an upper surface of a forward portion of the second rail member.

12. The rail assembly of claim 1, wherein the central region of the elongate loadbearing beam structure includes a through-going aperture formed between a lower portion of a center portion of the first rail member and an upper portion of a center portion of the second rail member.

13. The rail assembly of claim 1, wherein the second rail member includes a forward portion, a center portion, and a rear portion, and wherein the center portion extends further downward in a vertical direction than the forward portion and the rear portion.

14. The rail assembly of claim 13, wherein the second rail member includes a bottom flange extending inboard from a side wall of at least the center portion of the second rail member.

15. The rail assembly of claim 1, wherein a beam height of the elongate load-bearing beam structure varies over a longitudinal length of the elongate load-bearing beam structure, and includes a maximum height that is located in the central region between opposing ends of the elongate load-bearing beam structure.

16. The rail assembly of claim 1, wherein an upper surface of a forward region of the elongate load-bearing beam structure is offset to be lower than an upper surface of the central region and an aft region of the elongate load-bearing beam structure.

17. The rail assembly of claim 1, wherein a side wall of the second rail member is thinner than at least one of a bottom flange of the second rail member and a top flange of the second rail member.

18. The rail assembly of claim 1, wherein a side wall of the second rail member includes a planar inboard surface.

19. The rail assembly of claim 1, wherein an outboard surface at a center portion of the second rail member mates with an inboard surface of a rear portion of the first rail member, and an inboard surface at a forward portion of the second rail member mates with an outboard surface of the first rail member.

20. The rail assembly of claim 1, wherein the first rail member is configured to abut each of opposing inboard and outboard surfaces of the second rail member.

21. The rail assembly of claim 1, wherein the first rail member includes a compressive load capacity of at least 120 ksi.

22. The rail assembly of claim 1, wherein the second rail member includes a tensile load capacity of at least 220 ksi.

23. The rail assembly of claim 1, wherein the second material of the second rail member has a higher tensile strength than the first material of the first rail member.

24. The rail assembly of claim 1, wherein when subject to tensile stress, the second material of the second rail member is more resistant to cracking than the first material of the first rail member.

25. The rail assembly of claim 1, wherein the first material consists of aluminum.

26. The rail assembly of claim 1, wherein the second material consists of steel.

27. The rail assembly of claim 1, further comprising, for each rail, at least one reinforcement structure coupled to an inner side wall of the first rail member or an inner side wall of the second rail member, the at least one reinforcement structure configured to provide enhanced localized strength of the elongate load-bearing beam structure.

28. The rail assembly of claim 27, wherein at least one of the at least one reinforcement structure is fixedly coupled to a suspension assembly of the chassis frame of the tractor vehicle.

29. The rail assembly of claim 1, further comprising at least one cross-bracing beam fixedly coupled to and extending between the pair of rails, such that the at least one crossbracing beam is positioned in a region associated with a fifth-wheel connection assembly of the chassis frame.

30. A chassis frame including the rail assembly of claim 1, wherein the natural resonant frequency of the chassis frame is between 19 Hz and 24 Hz.

31. A collection of rail assemblies according to claim 1, and comprising a first rail assembly, a second rail assembly, and a third rail assembly, each rail assembly having identical front regions, identical rear regions, and different overall lengths.

32. A rail for a chassis frame of a tractor vehicle, the rail comprising: a first rail member formed of a first material; anda second rail member formed of a second material, the first rail member fixedly coupled to the second rail member to form an elongate load-bearing beam structure comprising different materials including the first material and the second material, wherein a density of the first material of the first rail member is less than a density of the second material of the second rail member, and wherein the elongate load-bearing beam structure is configured such that a compressive load is applied to the first rail member within a central region of the elongate load-bearing beam structure in static conditions and a tensile load is applied to the second rail member within the central region of the elongate load-bearing beam structure in the static conditions.

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