Increased-strength rear cradle for a land vehicle
Patent Information
- Application Number
- EP2023716636
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-04-21
- Filing Date
- 2023-03-17
- Publication Date
- 2025-02-26
AI Technical Summary
Rear cradles in land vehicles are prone to bending and potential damage during high-speed rear impacts, leading to risk of tearing of support points, battery damage, and electrical hazards due to the inability of existing structures to absorb the absorbed forces effectively.
A rear cradle with a box structure in its lower sub-part designed to absorb forces parallel to the longitudinal direction, utilizing steel or aluminum sheets of specific thicknesses, or composite materials, to prevent bending and ensure safety by distributing impact forces within a chosen threshold.
The reinforced rear cradle effectively absorbs forces up to a certain threshold, preventing bending and potential damage to the rear axle, battery, and electrical components, enhancing the vehicle's passive safety by reducing the risk of fire and electrocution.
Smart Images
Figure 1.1
Abstract
Description
[0001] DESCRIPTION
[0002] TITLE: REAR CRADLE WITH REINFORCED STRENGTH FOR A LAND VEHICLE
[0003] Technical field of the invention
[0004] The present invention claims priority from French application 2203695 filed on April 21, 2022, the content of which (text, drawings and claims) is incorporated herein by reference.
[0005] The invention relates to land vehicles, and more specifically to the rear cradles which are part of such vehicles (possibly within platforms).
[0006] State of the art
[0007] Some land vehicles, generally of the automobile type, comprise a structure (or possibly a platform) comprising a rear floor to which is secured a rear cradle comprising two lateral parts (right and left) to which are coupled respectively two lateral rear axle arms (right and left) and a rear drive machine forming part of a powertrain (or GMP). Generally, each lateral part of this rear cradle comprises a front part and a rear part connected by at least one upper tube and one lower tube between which is defined a passage adapted to the crossing and the travel of the transmission shaft of the rear drive machine.
[0008] In the foregoing and following, the concept of "front" is defined in relation to the front end of the vehicle, and the concept of "rear" is defined in relation to the rear end of the vehicle (opposite the front end). Therefore, the front part of an element is (intended to be) oriented towards the front end of the vehicle, while the rear part of that element is (intended to be) oriented towards the rear end of the vehicle.
[0009] When the vehicle is subjected to a rear impact at high speed with an object having a relatively small vertical extension, the rear subframe, with the equipment it supports or which is coupled to it, offers an additional contact surface which is added to the "main" contact surface offered by the rear end of the vehicle structure. Due to the weight and size of the rear subframe, the rear axle lateral arms and the rear drive machine, the impact of the object with the rear subframe can be violent (the force absorbed can typically be between 30 kN (or 3 tonnes) and 50 kN (or 5 tonnes)).As a result, this can cause the rear subframe to flex downwards in its front section, as the side section tubes (and in particular the lower tube) cannot absorb this force, and this can result in the rear axle mounting points and the drive unit chocks being torn off.
[0010] It should be noted that the situation can be even more problematic when the vehicle includes, slightly in front of the rear cradle, a main battery (supplying electrical energy to the rear drive machine when it is electric), because the bent front part of the rear cradle can damage the main battery which can prove dangerous in terms of electrical safety and / or pollution.
[0011] In addition, the rear drive unit's electrical power harness may become damaged or even exposed and come into contact with the vehicle structure, which may cause a fire and / or electrocution of a passenger or person working on the damaged vehicle.
[0012] The invention therefore aims in particular to improve the situation.
[0013] Presentation of the invention
[0014] It proposes in particular for this purpose a rear cradle, on the one hand, suitable for being secured to a lower face of a floor of a land vehicle comprising a rear axle with lateral arms and a rear drive machine having a transmission shaft coupled to this rear axle, and, on the other hand, comprising two lateral parts to which this rear drive machine and these lateral arms are intended to be secured respectively, and each comprising a passage adapted for the crossing and the movement of the transmission shaft.
[0015] This rear cradle is characterized by the fact that each lateral part has, at least in a lower sub-part delimiting a lower portion of the passage, a box structure capable of absorbing forces lower than a chosen threshold and resulting from an impact suffered from the rear by the land vehicle in a direction having a component parallel to a longitudinal direction.
[0016] Thanks to the invention, in the event of a rear impact, the rear cradle can now, due to its box structure at least in its lower sub-section, absorb forces lower than the chosen threshold, and therefore as long as the forces absorbed remain lower than this threshold there is no longer any risk of the rear cradle bending.
[0017] The rear cradle according to the invention may include other characteristics which may be taken separately or in combination, and in particular:
[0018] - in a first embodiment, each lateral part may comprise a main part delimiting a portion of the passage which is complementary to its lower portion, and on which the lower sub-part is attached;
[0019] - in a first embodiment, each lower sub-part may comprise an upper part having a generally inverted U-shaped section and a lower part fixedly secured to a lower end of this upper part, the upper part and lower part defining the box structure;
[0020] - in the presence of the last option, each lower sub-part may have a height in a vertical direction of the land vehicle which is between 25 mm and 45 mm, and a width in a transverse direction of the land vehicle which is between 80 mm and 100 mm;
[0021] - also in the presence of the last option, each lower sub-part can be made of steel from at least one sheet having a thickness between 1.5 mm and 2.5 mm. Alternatively, each lower sub-part can be made of aluminum from at least one sheet having a thickness between 2.5 mm and 4 mm.
[0022] - in a second embodiment, each lateral part may comprise first and second main flanges which are fixedly secured to each other and shaped so as to together define an overall box structure including the lower sub-part and at least partially delimiting the passage;
[0023] - in this second embodiment, the first and second main flanges of each lateral part can define an opening at the interface with an internal part of the passage, and each lateral part can comprise at least one auxiliary flange fixedly secured to the first and second main flanges and shaped so as to mask this opening in a sealed manner and to participate in the delimitation of the passage;
[0024] - also in this second embodiment, the first and second main flanges of each lateral part can each be made of steel from at least one sheet having a thickness of between 1.5 mm and 2.5 mm, or of aluminum from at least one sheet having a thickness of between 2 mm and 4 mm.
[0025] The invention also provides a land vehicle, possibly of the automobile type, and comprising:
[0026] - a floor,
[0027] - a rear axle with lateral arms,
[0028] - a rear drive machine having a transmission shaft coupled to this rear axle, and
[0029] - a rear cradle of the type presented above and to which this rear drive machine and these side arms are secured.
[0030] For example, the rear drive machine may be an electric machine powered by electric power from a main battery.
[0031] Brief description of the figures
[0032] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the attached drawings (obtained in CAD / CAM (“Computer Aided Design / Computer Aided Drawing”)), in which:
[0033] [Fig. 1] schematically illustrates, in a perspective view from below and partially in section in a longitudinal and vertical plane, a right rear part of an example of a motor vehicle comprising a right part of a first example of embodiment of a rear cradle according to the invention,
[0034] [Fig. 2] schematically illustrates, in a sectional view in a transverse and vertical plane, the right part of the rear cradle of figure 1,
[0035] [Fig. 3] schematically illustrates, in a perspective view from below and partially in section in a longitudinal and vertical plane, a right rear part of an example of a motor vehicle comprising a right part of a second example of embodiment of a rear cradle according to the invention, and
[0036] [Fig. 4] schematically illustrates, in a sectional view in a transverse and vertical plane, the right part of the rear cradle of figure 3.
[0037] Detailed description of the invention
[0038] The invention aims in particular to propose a rear cradle BR suitable for equipping a land vehicle VT and having reinforced (or increased) resistance so as to increase its capacity to absorb shocks from the rear, including at high speed.
[0039] In the following, it is considered, by way of non-limiting example, that the rear cradle BR is intended to be part of a land vehicle VT of the automobile type, such as for example a car. But the invention is not limited to this type of land vehicle. It in fact concerns any land vehicle comprising a rear floor to which a rear cradle is secured (to which a rear drive machine forming part of a GMP and two lateral arms of a rear axle are coupled), and capable of undergoing impacts from the rear.
[0040] Furthermore, it is considered, by way of non-limiting example, that the rear drive machine is an electric machine (or motor) responsible for rotating the wheels of at least one rear axle using the electrical energy supplied by a main (or traction) battery installed in its underbody (here under the floor). Consequently, the GMP is of the all-electric or hybrid (thermal and electric) type.
[0041] In Figures 1 to 4, the X direction is the longitudinal direction of the vehicle VT, which is parallel to the lateral (or longitudinal) sides comprising the side doors, the Y direction is the transverse direction of the vehicle VT, which is perpendicular to the longitudinal direction X, and the Z direction is the vertical direction of the vehicle VT, which is perpendicular to the longitudinal X and transverse Y directions.
[0042] Figures 1 and 2 schematically illustrate right rear parts of examples of land vehicles VT, which respectively comprise (right) parts of first and second examples of embodiment of a rear cradle BR according to the invention.
[0043] As partially illustrated, the vehicle VT comprises in its rear part a PLV floor comprising a lower face Fl to which is fixedly secured a rear cradle BR to which is coupled in particular a rear drive machine MM (here an electric motor) of the GMP, responsible for rotating at least the rear wheels of the rear axle. For this purpose, the rear drive machine MM has a transmission shaft AT which is coupled to the rear axle. This rear drive machine MM produces torque (for rotating the transmission shaft AT) from the electrical energy which is stored in a main (or traction) battery installed in its underbody (for example under the PLV floor).
[0044] Note that the lower face Fl of the PLV floor is oriented downwards (or the ground) and is opposite an upper face which is oriented upwards.
[0045] The rear wheels (right and left) are coupled respectively to two lateral arms BL (right and left) of the rear axle, which are also coupled to lateral parts PLB (right and left) of the rear subframe BR. These lateral parts PLB are for example coupled to each other via a front cross member TV and a rear cross member TR which extend in the transverse direction Y.
[0046] As illustrated in Figures 1 to 4, each of the two lateral parts PLB of the rear cradle BR comprises a passage PA which is adapted to the crossing and the movement of the transmission shaft AT. In addition, each lateral part PLB has, at least in a lower sub-part SPI delimiting a lower portion of the passage PA, a box structure which is capable of absorbing forces lower than a chosen threshold sc and which result from an impact suffered from the rear by the vehicle VT in a direction having a component parallel to the longitudinal direction X of the vehicle VT.
[0047] Thus, when the vehicle VT is subjected to a rear impact (possibly at high speed) with an object having a relatively small vertical extension, the rear subframe BR can now, due to its box structure at least in its lower sub-part SPI, absorb the forces resulting from this impact, provided that these forces are lower than the chosen threshold sc. Consequently, as long as the forces remain lower than sc, there is no longer any risk of the rear subframe BR bending, and therefore of the rear axle attachment points and the chocks of the rear drive unit MM being torn off. Furthermore, in the presence of a main battery located slightly in front of the rear subframe BR, there is no longer any risk that the latter (BR) will damage this main battery as long as the forces remain lower than sc.In addition, since the rear cradle BR remains (almost) integrated as long as the forces remain lower than sc, there is no longer any risk that the electrical power supply harness of the rear drive machine MM will be damaged or even stripped, which makes it possible to avoid a fire and / or electrocution of a passenger or a person working on the damaged vehicle VT.
[0048] The invention therefore makes it possible to reinforce the passive safety offered by the VT vehicle.
[0049] For example, the box structure of the BR rear cradle can be arranged and dimensioned so that it can withstand forces lower than a chosen threshold sc between 30 kN (or 3 tonnes)) and 70 kN (or 7 tonnes)), and more preferably between 50 kN (or 3 tonnes)) and 70 kN (or 7 tonnes)).
[0050] At least two embodiments can be envisaged for the BR rear cradle.
[0051] In a first embodiment illustrated in Figures 1 and 2, each lateral part PLB of the rear cradle BR comprises a main part PP and the lower sub-part SPI. The main part PP delimits a portion of the passage PA which is complementary to its lower portion (delimited by the lower sub-part SPI), and the latter (SPI) is attached to the main part PP and has the box structure which allows the rear cradle BR to absorb forces lower than the chosen threshold sc. It will be understood that in this first embodiment the main part PP does not necessarily have a box structure, although this is possible at least in at least one of its sub-parts (such as for example in its upper sub-part which delimits the upper portion of the passage PA).
[0052] Preferably, each lower SPI sub-part is fixedly secured to the associated main PP part by welding. But screwing can also be considered.
[0053] In an alternative embodiment not illustrated, each lateral part PL could be in one piece, and in this case its lower sub-part SPI and its main part PP extend each other, with of course the condition that at least the lower sub-part SPI has a box structure.
[0054] As illustrated non-limitingly in Figures 1 and 2, the lower sub-part SPI may comprise an upper part PSS and a lower part PIS. As illustrated non-limitingly in Figure 2, the upper part PSS may have a generally inverted U-shaped section, and in this case comprises a downwardly oriented opening. The lower part PIS is fixedly secured to the lower end of the upper part PSS, which closes the opening of the upper part PSS. Thus, the upper part PSS and lower part PIS together define a box structure capable of absorbing (or supporting) very significant forces (less than sc) in the event of an impact suffered from the rear by the vehicle VT in a direction having a component parallel to the longitudinal direction X.
[0055] For example, the lower SPI sub-part may have a height in the vertical Z direction that is between 25 mm and 45 mm. As an illustrative example, this height may be equal to 35 mm.
[0056] Also for example, the lower SPI sub-part may have a width along the transverse direction Y which is between 80 mm and 100 mm. As an illustrative example, this width may be equal to 90 mm.
[0057] Also for example, the lower SPI sub-part can be made of steel from at least one sheet. Thus, this steel can be of type S420MC. In this case, this (each) steel sheet can, for example, have a thickness which is between 1.5 mm and 2.5 mm. As an illustrative example, this thickness can be equal to 2 mm. It will be noted that when the lower SPI sub-part comprises a PSS upper part and a PIS lower part, the steel sheets from which they are made can possibly have different thicknesses.
[0058] Alternatively, the lower SPI sub-part may be made of aluminum from at least one sheet. Thus, this aluminum may be of type T6-6061. In this case, this (each) aluminum sheet may, for example, have a thickness that is between 2.5 mm and 4 mm. It will be noted that when the lower SPI sub-part comprises a PSS upper part and a PIS lower part, the aluminum sheets from which they are made may possibly have different thicknesses. As an illustrative example, the thickness of the PSS upper part may be equal to 3.5 mm and the thickness of the PIS lower part may be equal to 3 mm.
[0059] In another variant, the lower SPI sub-section (box structure) could be made from a very strong composite material.
[0060] In a second embodiment illustrated in Figures 3 and 4, each lateral part PLB of the rear cradle BR comprises first FP1 and second FP2 main flanges which are fixedly secured to each other. In addition, and as is better shown in Figure 4, these first FP1 and second FP2 main flanges are shaped so as to together define an overall box structure which includes the lower sub-part SPI and at least partially delimits the passage PA. This second embodiment advantageously allows the rear cradle BR to absorb forces lower than a chosen threshold sc which is possibly higher than in the first embodiment, or to absorb forces similar to those of the first embodiment but with sub-parts of its lateral parts PLB having smaller dimensions than those of the lower sub-part SPI of the first embodiment.
[0061] Preferably, the first FP1 and second FP2 main flanges of each PLB side part are fixedly secured to each other (possibly with an edge overlap) by welding.
[0062] For example, and as illustrated non-limitingly in Figures 3 and 4, the first FP1 and second FP2 main flanges of each lateral part PLB may define an opening at the interface with the internal part of the passage PA. In this case, each lateral part PLB may comprise at least one auxiliary flange FA fixedly secured to the first FP1 and second FP2 main flanges and shaped so as to mask this opening in a sealed manner and to participate in the (internal) delimitation of the passage PA. This arrangement makes it possible to simplify the production of each of the first FP1 and second FP2 main flanges, and to prevent elements (liquids or small bodies) from penetrating and accumulating inside the lateral parts PLB. In addition, each auxiliary flange FA may also possibly participate in the solidity and resistance of its lateral part PLB.
[0063] Preferably, each auxiliary flange FA is fixedly secured by welding to the first FP1 and second FP2 associated main flanges.
[0064] For example, each of the first FP1 and second FP2 main flanges may be made of steel from a sheet. Thus, this steel may be of type S420MC. In this case, this steel sheet may, for example, have a thickness which is between 1.5 mm and 2.5 mm. As an illustrative example, this thickness may be equal to 2 mm.
[0065] Alternatively, each of the first FP1 and second FP2 main flanges may be made of aluminum from a sheet. Thus, this aluminum may be of type T6-6061. In this case, this aluminum sheet may, for example, have a thickness which is between 2 mm and 4 mm. As an illustrative example, this thickness may be equal to 3.5 mm.
[0066] Also for example, each possible auxiliary flange FA can be made of steel from a sheet. Thus, this steel can be of type S420MC. In this case, this steel sheet can, for example, have a thickness which is between 1 mm and 2 mm. As an illustrative example, this thickness can be equal to 1.5 mm.
[0067] Alternatively, each possible auxiliary flange FA may be made of aluminum from a sheet. Thus, this aluminum may be of type T6-6061. In this case, this aluminum sheet may, for example, have a thickness which is between 1.5 mm and 3 mm. As an illustrative example, this thickness may be equal to 2.5 mm.
Claims
DEMANDS 1. Rear cradle (BR) suitable for being attached to an underside (Fl) of a floor (PLV) of a land vehicle (VT) comprising a rear axle with lateral arms (BL) and a rear drive unit (MM) having a transmission shaft (AT) coupled to said rear axle, said rear cradle (BR) comprising two lateral parts (PLB) to which said rear drive unit (MM) and said lateral arms (BL) are intended to be attached respectively and each comprising a passage (PA) adapted for the passage and movement of said transmission shaft (AT), characterized in that each lateral part (PLB) has, at least in a lower sub-part (SPI) delimiting a lower portion of said passage (PA), a box-section structure suitable for absorbing forces below a chosen threshold and resulting from an impact suffered by the rear of said land vehicle (VT) in a direction having a component parallel to a longitudinal direction.
2. Rear cradle according to claim 1, characterized in that each lateral part (PLB) comprises a main part (PP) delimiting a portion of said passage (PA) which is complementary to its lower portion, and on which said lower sub-part (SPI) is attached.
3. Rear cradle according to claim 2, characterized in that said lower sub-part (SPI) comprises an upper part (PSS) having a cross-section in the general shape of an inverted U and a lower part (PIS) fixedly attached to a lower end of said upper part (PSS), said upper part (PSS) and lower part (PIS) defining said box structure.
4. Rear cradle according to claim 3, characterized in that said lower sub-part (SPI) has a height along a vertical direction of said land vehicle (VT) of between 25 mm and 45 mm, and a width along a transverse direction of said land vehicle (VT) of between 80 mm and 100 mm.
5. Rear cradle according to claim 3 or 4, characterized in that said lower sub-part (SPI) is made of steel from at least one sheet having a thickness between 1.5 mm and 2.5 mm.
6. Rear cradle according to claim 3 or 4, characterized in that said lower sub-part (SPI) is made of aluminium from at least one sheet having a thickness between 2.5 mm and 4 mm.
7. Rear cradle according to claim 1, characterized in that each lateral part (PLB) comprises first (FP1) and second (FP2) main flanges fixedly joined to each other and shaped to define together an overall box structure including said lower sub-part (SPI) and at least partially delimiting said passage (PA).
8. Rear cradle according to claim 7, characterized in that said first (FP1) and second (FP2) main flanges of each lateral part (PLB) define an opening at the interface with an internal part of said passage (PA), and in that each lateral part (PLB) comprises at least one auxiliary flange (FA) fixedly attached to said first (FP1) and second (FP2) main flanges and shaped so as to hermetically seal said opening and to participate in the delimitation of said passage (PA).
9. Rear cradle according to claim 7 or 8, characterized in that said first (FP1) and second (FP2) main flanges are each made of steel from at least one sheet having a thickness between 1.5 mm and 2.5 mm, or of aluminium from at least one sheet having a thickness between 2 mm and 4 mm.
10. Land vehicle (VT) comprising a floor (PLV), a rear axle with lateral arms (BL) and a rear drive unit (MM) having a transmission shaft (AT) coupled to said rear axle, characterized in that it further comprises a rear cradle (BR) according to one of the preceding claims, to which said rear drive unit (MM) and said lateral arms (BL) are attached.