Axial crush member

Abstract

A vehicle 100 has first and second rear longitudinal members 102, 104 extending rearwards on respective first and second sides of the vehicle and a laterally-extending rear crossmember 118 connected to, and extending between, rear longitudinal members 102, 104. At least one axial crush member 134 is connected to rear crossmember 118, and extends longitudinally and rearwards between rear longitudinal members 102, 104. During a rear impact of sufficiently high energy, crush member 134 crushes in the longitudinal direction while transferring load to crossmember 118. Preferably, crush member 134 is within a central 50% of the vehicle body width, and may extend along a midline of the vehicle. Longitudinal formations such as flanges, folds, undulations, corrugations or ribs may be provided in crush member 134. Crush member 134 may be connected to the underside of a vehicle floor panel 110. Vehicle 100 may be a battery electric vehicle with a traction battery.

Description

TECHNICAL FIELD The present disclosure relates to an axial crush member and a vehicle comprising such an axial crush member. BACKGROUND It is known to provide vehicles with crumple zones to help absorb and dissipate energy in the event of an impact with an object or another vehicle. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide an axial crush member and a vehicle comprising an axial crush member, as claimed in the appended claims According to an aspect of the present invention there is provided a vehicle comprising: a first rear longitudinal member extending rearwards on a first side of the vehicle; a second rear longitudinal member extending rearwards on a second side of the vehicle opposite the first side; a laterally-extending rear crossmember connected to, and extending between, the first rear longitudinal member and the second rear longitudinal member; and at least one axial crush member connected to the rear cross member, the at least one axial crush member extending longitudinally and rearwards between the first rear longitudinal member and the second rear longitudinal member; the at least one axial crush member being configured such that, during a rear impact of sufficiently high energy, the at least one axial crush member crushes in the longitudinal direction while transferring load to the crossmember. By dissipating energy and transferring load to the crossmember, the axial crush member may improve rear-end collision performance. The at least one axial crush member may be at least partly disposed within a central 50% of a width of a body of the vehicle, or entirely disposed within a central 50% of a width of a body of the vehicle. Limiting the width of the axial crush member may offer a lighter and / or more compact implementation. The at least one axial crush member comprises at least one axial crush member extending along a midline of the vehicle. The at least one axial crush member may comprise one or more longitudinal formations to increase longitudinal stiffness. The one of more formations may comprise one or more flanges, folds, undulations, corrugations, or ribs. This may improve energy transfer to the rear crossmember. The one or more longitudinal formations may be entirely disposed within a central 50% of a width of a body of the vehicle. The at least one axial crush member may comprise a longitudinal web, the one or more formations comprising longitudinally extending flanges extending along laterally outer edges of the web. The at least one axial crush member may be substantially U-shaped or have a box section along at least a majority of its length. The at least one axial crush member may be attached to an underside of a horizontally extending body panel. This may help stabilize the axial crush member as it crushes in the event of a rear impact. The body panel may be a lower floor or subfloor panel of a boot, trunk, or storage compartment at a rear of the vehicle. The vehicle may be a battery electric vehicle comprising a traction battery. According to a further aspect of the present invention, there is provided an axial crush member for use with the vehicle of the preceding aspect. The axial crush member may be configured for attachment to the rear crossmember, and / or to abut a rearward surface of the rear crossmember. The axial crush member may comprise one or more longitudinal formations to increase longitudinal stiffness. The one of more formations may comprise one or more flanges, folds, undulations, corrugations, or ribs. The one axial crush member may comprise a longitudinal web, the one or more formations comprising longitudinally extending flanges extending along laterally outer edges of the web. The axial crush member may be substantially U-shaped or have a box section along at least a majority of its length. The axial crush member may be configured for attachment to an underside of a horizontally extending body panel. The axial crush member may be generally trapezoidal in plan. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an underside view of a vehicle having rear longitudinal members, and a rear impact barrier; Figure 2 is an underside view of the vehicle of Figure 1 after impact with the rear impact barrier; Figure 3 is an underside view of a vehicle comprising a vehicle sub-assembly comprising an axial crush member, according to an embodiment of the invention, and a rear impact barrier; Figure 4 is an underside view of the vehicle of Figure 3 after impact with the rear impact barrier; Figure 5 is an underside view of an axial crush member according to an embodiment of the invention; Figure 6 is a schematic cross-section taken across lines VI-VI of the axial crush member of Figure 5; Figure 7 is a perspective view of a vehicle comprising a vehicle sub-assembly, in accordance with an embodiment in the invention; Figures 8 to 10 are schematic cross-sections of axial crush members according to further embodiments of the invention; and Figures 11 to 13 are schematic underside views of vehicles comprising vehicle sub-assemblies comprising axial crush members, according to further embodiments of the invention. DETAILED DESCRIPTION Figures 1 and 2 show a prior art vehicle sub-assembly in the form of a unibody chassis 300 of a vehicle. The chassis 300 forms part of a vehicle, but many of the vehicle’s other components, such as the rear subframe, suspension and drivetrain components, axles, wheels, and tyres, are omitted for clarity. The chassis 300 includes a left rear longitudinal member 302 and a right rear longitudinal member 304 (noting that Figures 1 and 2 show the underside rear end of the chassis 300). The left rear longitudinal member 302 and the right rear longitudinal member 304 are indicated with hatching to show them more clearly relative to the surrounding chassis. The left rear longitudinal member 302 and the right rear longitudinal member 304 extend rearwardly between respective wheel arches 306 and 308. A body panel in the form of a subfloor panel 310 extends between inner edges of the longitudinal members 302 and 304. The subfloor panel 310 defines part of a lower region of a storage well 312 for a spare wheel (not shown). Stamped ribs 314 help stiffen the storage well 312 and the subfloor panel 310 more generally. A rear crossmember 318 extends between inner edges of the longitudinal members 302 and 304. The rear crossmember 318 increases lateral stiffness and strength of the chassis 300. The longitudinal members 302 and 304 include respective rear subframe mounting points 320 and 322, to which a rear subframe (not shown, for clarity) is mounted. The longitudinal members 302 and 304, wheel arches 306 and 308, subfloor panel 310, and rear cross member 318 are formed from stamped (or otherwise formed) steel and / or aluminium alloy, although other manufacturing techniques and / or materials may be employed. The various components are integrally joined to each other and surrounding bodywork to form the unibody chassis 300. The various elements can be joined to each other by way of, for example, welding, adhesives, connectors such as rivets, self-piercing rivets, screws, or bolts, or any suitable combination of such joining mechanisms. At least some of the components can be formed from a common sheet or piece of metal or other material. A rear impact barrier 324 is shown to the rear of chassis 300. The rear impact barrier 324 is moving in the direction of arrow 326 as part of a rear collision test. Different forms of rear collision test exist in different jurisdictions. For example, in the US, one rear collision test (FMVSS314) includes hitting a stationary vehicle with a rear impact barrier (such as rear impact barrier 324) having a mass of 1368 kg, at a speed of 55 miles per hour. The rear impact barrier 324 is positioned such that, at impact, it extends 70% across the width of the vehicle. The vehicle width is indicated by arrow 328, and 70% of the vehicle width is indicated by arrow 330. Although not shown or described herein, it will be appreciated that such tests are performed on the left and right sides of a vehicle. Different rear offset impact tests may be used in different jurisdictions. Figure 2 shows the chassis 300 after the test. The rear impact barrier 324 has impacted the left rear of chassis 300, significantly crushing it on the left side of impact. Significant energy is dissipated as the various elements of the chassis deform during the impact. In particular, the relatively strong and stiff left longitudinal member 302 absorbs and transfers significant energy. There is some deformation of the right hand side of the chassis 300, but the rear impact barrier 324 does not directly impact it during the test. Some energy will be transmitted to the right rear longitudinal member 304 through the the rear crossmember 318, but this will be limited due to the distance of the left rear longitudinal member 302 from the right rear longitudinal 304 and the way in which the rear part of left rear-longitudinal member 302 absorbs energy by deforming during a rear impact. Turning to Figures 3 and 4, there is shown a vehicle sub-assembly in accordance with an embodiment of the present invention. The vehicle sub-assembly can form part of a vehicle, such as vehicle 200 as shown in Figure 7. The sub-assembly takes the form of a unibody chassis 100 of a vehicle, but in other embodiments, can take the form of a rear sub-assembly that is joined to one or more other sub-assemblies to form the chassis 100. The chassis 100 forms part of a vehicle, such as vehicle 200, but many of the vehicle’s other components, such as the rear subframe, suspension and drivetrain components, axles, wheels, and tyres, are omitted from Figures 3 and 4 for clarity. The chassis 100 includes a left rear longitudinal member 102 and a right rear longitudinal member 104 (noting that Figures 3 and 4 show the underside of the rear end of chassis 100). The left rear longitudinal member 102 and the right rear longitudinal member 104 are indicated with hatching to show them more clearly relative to the surrounding chassis. The left rear longitudinal member 102 and the right rear longitudinal member 104 extend rearwardly between respective wheel arches 106 and 108. A body panel in the form of a subfloor panel 110 extends between inner edges of the longitudinal members 102 and 104. The subfloor panel 110 defines part of a lower region of a storage well 112 for a spare wheel (not shown). Stamped ribs 114 help stiffen the storage well 112 and the subfloor panel 110 more generally. A forward rear crossmember 116 and a rearward rear crossmember 118 extend between inner edges of the rear longitudinal members 102 and 104. The forward rear crossmember 116 and the rearward rear crossmember 118 increase lateral stiffness and strength of the chassis 100, The longitudinal members 102 and 104 include respective rear subframe mounting points 120 and 122, to which a rear subframe (not shown, for clarity) is mounted. The longitudinal members 102 and 104, wheel arches 106 and 108, subfloor panel 110, forward rear crossmember 116 and rearward rear crossmember 118 are formed from stamped (or otherwise formed) steel and / or aluminium alloy, although other manufacturing techniques and / or materials may be employed. The various components are integrally joined to each other and surrounding bodywork to form the unibody chassis 100. The various elements can be joined to each other by way of, for example, welding, adhesives, connectors such as rivets, self-piercing rivets, screws, or bolts, or any suitable combination of such joining mechanisms. At least some of the components can be formed from a common sheet or piece of metal or other material. As such, there is little fundamental difference with the chassis 300 of Figures 1 and 2. However, here, an axial crush member 132 is disposed underneath the subfloor panel 110. The axial crush member 132 is disposed in a generally horizontal plane and extends longitudinally and rearwards from the rear crossmember 118, between the rear longitudinal members 102 and 104. One embodiment of the axial crush member 132 is shown in Figures 5 and 6. The axial crush member 132 is generally trapezoidal in plan view, narrowing towards the rear of the vehicle. As best shown in Figure 6, the axial crush member 132 is substantially U-shaped along at least a majority of its length. This helps increase stiffness in the longitudinal direction. In other embodiments, the axial crush member can have a box, triangular, or trapezoidal section along at least a majority of its length. The axial crush member 132 comprises a longitudinal web 134, and longitudinally extending flanges 136 extending along lateral outer edges of the web 134, The flanges 136 are a form of longitudinal formation that increases stiffness of the axial crush member 132 in the longitudinal direction. Additional flanges 138 extend laterally from flanges 136. Lateral stiffening ribs 140 extend outwardly from the flanges 136 onto the additional flanges 138 to provide additional strength and rigidity. A forward edge 142 of the web 134 extends beyond the flanges 136 to overlap, when installed, a lower surface of the rear crossmember 118. The forward edge 142 can optionally be attached to the underside of the rear crossmember 118, such as by way of self-piercing rivets or any other joining mechanism or method. Abutment elements 144 extend from the end of the flanges 136 to abut a rearward surface of the rear crossmember 118. The abutment elements 144 can optionally be attached to the rear of the rear crossmember 118, such as by way of self-piercing rivets or any other joining mechanism or method. Similar abutment elements 146 extend from the opposite end of the flanges 136 to abut a body panel, such as a rear panel (not shown). The abutment elements 146 can optionally be attached to the body panel by way of self-piercing rivets or any other joining mechanism or method. As best shown in Figure 3, the axial crush member 132 is attached, at its forward end, to the rear crossmember 118. The attachment can be made in any suitable manner, including using fasteners such as bolts, screws, or rivets, welding of any suitable type, and / or bonding, for example. In the embodiment shown, self-piercing rivets (not shown) pass through the forward edge 142 into the lower surface of the rear crossmember 118. The axial crush member 132 can be attached to an underside of a horizontally extending body panel, such as a lower floor or subfloor panel of a boot, trunk, or storage compartment at a rear of the vehicle. In the embodiment shown, the axial crush member 132 is attached to the subfloor panel 110 byway of the additional flanges 138. The attachment can be made in any suitable manner, including using fasteners such as bolts, screws, or rivets, welding of any suitable type, and / or bonding, for example. In the embodiment shown, selfpiercing rivets (not shown) pass through the additional flanges 138 into the subfloor panel 110. The axial crush member 132 is configured, during a rear impact of the vehicle, to crush in the longitudinal direction while transferring load to the rear crossmember 118. Figure 4 shows the chassis 100 after rear impact testing. The rear impact barrier 324 has impacted the rear of chassis 100, significantly crushing it on the left side of impact. Significant energy is dissipated as the various elements of the chassis deform due to the impact. As in the example of Figures 1 and 2, the relatively strong and stiff left longitudinal member 102 absorbs and transfers significant energy. In addition, the axial crush member 132, being positioned centrally relative to the width of the chassis 100, absorbs energy by crushing, and transfers significant energy to the centre of the rear crossmember 118. The rear crossmember 118 transfers more energy to the right rear longitudinal member 104 than was the case in the example of Figures 1 and 2. The coupling between the axial crush member 132, the rear crossmember 118, and the subfloor panel 110, helps reduce displacement of the axial crush member 132 during impact, which can increase the amount of energy that is absorbed and transferred in the forward direction. By dissipating energy and transferring load to the crossmember, the axial crush member may improve safety in the event of a rear-end collision. Comparing the post impact damage in Figure 2 (prior art) and Figure 4 (an embodiment of the invention), it will be seen that in Figure 4, significantly more damage is caused to the right rear longitudinal member 104 as a result of the increased energy transfer through the axial crush member 132 and the rear crossmember 118. Similarly, the transfer of energy to the rear crossmember 118 and the right rear longitudinal member 104 means that there is less damage to the left rear longitudinal member 102 in Figure 4, which means, among other things, that the left mounting point 120 is not pushed back as far as was the case with left mounting point 320 in Figure 2. This means that the rear subframe (not shown, for clarity) that is mounted to the mounting points 120 / 320 will not be pushed forward as far or hard in Figure 4 as in Figure 2. This may reduce the chance of damage to structures in front of the rear subframe. The rear crossmember 118 is also more damaged in Figure 4, as are the structures 164 of the chassis 100 immediately forward of the rear crossmember 118. The additional damage is caused by the transfer of additional energy to these components and regions. The net result of this transfer is that the left rear longitudinal member 102 in Figure 4 (and the immediately surrounding bodywork 106) absorbs less of the energy of the impact compared to the left rear longitudinal 302 in Figure 2. The result is reduced deformation on the left side of the vehicle. Other forms of longitudinal formations can optionally be provided to help improve performance of the axial crush member 132. For example, one or more further flanges can be provided. One or more longitudinal folds, undulations, corrugations, ribs, or the like can optionally be provided along the axial crush member. For example, Figure 8 shows a cross-section of an axial crush member that has a longitudinal fold 142, Figure 9 shows a cross-section of an axial crush member that has longitudinal corrugations 144, and Figure 10 shows a cross section of an axial crush member that has longitudinal ribs 146. Any other types, numbers and / or combinations of longitudinal formations can be implemented to suit the needs of a particular application. Turning to Figures 11 to 13, there are shown a number of different embodiments of vehicle sub-assemblies including rear axial crush members. These embodiments represent non-limiting examples of configurations, positions, orientations, and combinations of rear axial crush members. Figures 11 to 13 also show various relationships that can exist between a width 150 of the vehicle 100 and the lateral extent(s) of the axial crush member(s) and their sub-components. Figure 11 shows an embodiment having a single axial crush member 132 as described above with reference to Figures 3 and 4. The axial crush member 132 is positioned centrally relative to the width 150 of the vehicle. Arrow 152 indicates a central 50% of width 150, arrow 154 indicates a maximum lateral extent of the axial crush member 132, and arrow 156 indicates a maximum lateral extent of the longitudinal formations (i.e., flanges 136 in the illustrated embodiment). In the embodiment of Figure 11, the flanges 136 are entirely disposed within the central 50% of the vehicle s body-width. In this case, the axial crush member 132 is entirely disposed within the central 50% of the vehicle’s body-width, although in other embodiments only part of the axial crush member (such as the web, orweb and flanges, where provided) is disposed within the central 50% of the vehicle’s body-width. The embodiments described so far use only a single axial crush member 132, extending along the vehicle midline. In other embodiments, two or more axial crush members can be used. Optionally, at least one of the axial crush members extends along the vehicle midline, but in other embodiments, there is no axial crush member extending along the vehicle midline. Figure 12 shows an embodiment having two axial crush members 132. These can be of a similar size and configuration as the previously described axial crush member. However, the use of more than one axial crush member may allow narrower and / or less robust axial crush members to be used. In Figure 12, the axial crush members 132 are positioned equidistant from the vehicle midline, although in other embodiments the axial crush members can be different distances from the midline. In the embodiment of Figure 12, the two axial crush members 132 are both entirely disposed within the central 50%, indicated by arrows 152, of width 150, although in other embodiments only part of the axial crush members 132 (such as the web, or web and flanges, where provided) are disposed within the central 50% 152. A maximum lateral extent 156 of the longitudinal formations (i.e., flanges 136 in the illustrated embodiment) is also entirely disposed within the central 50% 152. Figure 13 shows another embodiment having a single axial crush member 132. The axial crush member 132 is positioned centrally relative to the distance, measured along the rear crossmember 118 and indicated by arrow 158, between inner edges of the left and right longitudinal members 102, 104. Arrow 160 indicates a central 50% of width 158, and arrow 162 indicates a maximum lateral extent of the axial crush member 132. In the embodiment of Figure 13, the axial crush member 132 is entirely disposed within the central 50% 160 of width 158, although in other embodiments only part of the axial crush member (such as the web, orweb and flanges, where provided) is disposed within the central 50% 160. Although not indicated with arrows for the sake of clarity, a maximum lateral extent of the longitudinal formations (i.e., flanges 136 in the illustrated embodiment) may also be entirely disposed within the central 50% 160. Multiple axial crush members falling within the central 50% indicated by arrows 160 can also be used, for example as described above with reference to Figure 12. In other embodiments, the figure of a central 50% of the vehicle width or of the distance between inner edges of the rear longitudinal members 102 and 104 can be reduced to 35% or even 20% of the vehicle width. By further constraining the lateral extent of at least the longitudinal formations, and optionally the entirety of the axial crush member(s), within these percentages, the axial crush member can be made more compact while still improving rear impact performance. The shape, configuration, size, materials, and position(s) of the axial crush member(s) can be optimized based on a desired or required performance, taking into account vehicle weight and the cost of producing and installing the rear longitudinal member(s). Based on the teaching within this patent application, the skilled person is able to perform this optimization using known design and modelling tools. Optionally, the vehicle 200 is a battery electric vehicle or a hybrid vehicle comprising a traction battery. Such vehicles are typically heavier than an internal combustion engine equivalent. They therefore tend to absorb more energy in a rear impact before they start to move, making it more important that energy is adequately absorbed and transferred. The use of an axial crush member as described herein can assist with the absorbing and transfer of energy during a rear impact. Optionally, the traction battery and / or associated circuitry are located between front axles and rear axles of the vehicle. For example, the traction battery can be horizontally planar and positioned just forward of the forward rear crossmember 116. It is important to protect the traction battery active material and key circuitry from damage during collisions. By improving the absorption of energy and the transfer of energy to the longitudinal members, the axial crush component described herein can reduce the chance of a rear impact causing damage to a rear section of the traction battery or its associated circuitry. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A vehicle comprising:a first rear longitudinal member extending rearwards on a first side of the vehicle;a second rear longitudinal member extending rearwards on a second side of the vehicle opposite the first side;a laterally-extending rear crossmember connected to, and extending between, the first rear longitudinal member and the second rear longitudinal member; andat least one axial crush member connected to the rear cross member, the at least one axial crush member extending longitudinally and rearwards between the first rear longitudinal member and the second rear longitudinal member;the at least one axial crush member being configured such that, during a rear impact of sufficiently high energy, the at least one axial crush member crushes in the longitudinal direction while transferring load to the crossmember.

2. The vehicle of claim 1, wherein the at least one axial crush member is at least partly disposed within a central 50% of a width of a body of the vehicle.

3. The vehicle of claim 2, wherein the at least one axial crush member is entirely disposed within a central 50% of a width of a body of the vehicle.

4. The vehicle of any preceding claim, wherein the at least one axial crush member comprises at least one axial crush member extending along a midline of the vehicle.

5. The vehicle of any preceding claim, wherein the at least one axial crush member comprises one or more longitudinal formations to increase longitudinal stiffness.

6. The vehicle of claim 5, wherein the one of more formations comprise one or more flanges, folds, undulations, corrugations, or ribs.

7. The vehicle of claim 5 or 6, wherein the one or more longitudinal formations are entirely disposed within a central 50% of a width of a body of the vehicle.

8. The vehicle of claim 7, wherein the at least one axial crush member comprises a longitudinal web, the one or more formations comprising longitudinally extending flanges extending along laterally outer edges of the web.9, The vehicle of any preceding claim, wherein the at least one axial crush member is substantially U-shaped or has a box section along at least a majority of its length.

10. The vehicle of any preceding claim, wherein the at least one axial crush member is attached to an underside of a horizontally extending body panel.

11. The vehicle of claim 10, wherein the body panel is a lower floor or subfloor panel of a boot, trunk, or storage compartment at a rear of the vehicle.

12. The vehicle of claim 11, in the form of an battery electric vehicle comprising a traction battery.10Application No: GB2405160.9 Examiner: Simon RoseClaims searched: 1-12Date of search: 11 September 2024Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-12 US 2009 / 0278384 Al (YAMADA et al) See particularly Figures 1-2, crush member 5, and paragraphs 23-28 X 1-3, 5-7, 10-12 CN 215883809 U (GREAT WALL MOTOR) See particularly Figure 1, force transmission beams 4 X 1-4, 9-12 JP 2009132260 A (MAZDA) See particularly Figure 1, crash can 27 X 1-2, 4, 9-12 JP 2002331965 A (NISSAN) See particularly Figures 2 and 4 and paragraphs 38, 40, 42 and 47 A - US 2004 / 0100127 Al (SAITOU) See particularly Figure 1, connecting member 15 A - US 2007 / 0182873 Al (BACCOUCHE) See particularly Figures 2-4Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From B62D 0021 / 15 01 / 01 / 2006

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