Front cradle of a motor vehicle

Abstract

The invention relates to a front subframe (12) extending from a chassis structural element of a motor vehicle, extending under an engine compartment to a front end. Said front subframe (12) comprises: - a rear crossmember (14) extending transversely and connected to said chassis structural element; - two arms (16, 18) integral with said rear crossmember (14) and extending longitudinally in a direction substantially perpendicular to said rear crossmember, each of said two arms (16, 18) having an end (20, 22) opposite said rear crossmember (14), and connected to said front end of said motor vehicle. Each of said two arms (16, 18) has a constricted zone (32, 30) to break at said constricted zone when said front end of said vehicle strikes an obstacle. Figure to be published with the abbreviation: Fig. 2

Description

Title of the invention: Front cradle for a motor vehicle

[0001] The present invention relates to a motor vehicle cradle adapted to be installed at the front of the vehicle.

[0002] Known front subframes are commonly used at the front of motor vehicles under their engine compartment and as an extension of the chassis structure. These subframes are further extended towards the front of the vehicle to the bumper or bumper, incorporating compressible structures to absorb front impacts and dissipate the energy they generate.

[0003] The cradles generally have a rear cross member attached to a structural element of the chassis, which cross member extends transversely within the vehicle, approximately directly above its bulkhead. They also have two arms attached to the rear cross member, which extend longitudinally towards the front of the vehicle. Two extensions then extend, respectively, in line with the two arms, to the compressible structure, which they may themselves incorporate.

[0004] Typically, the cradles are made of steel using welded sheet metal, as are the compressible structures located at the front. The steels used to make the latter have high plastic deformation capacities in order to absorb large amounts of energy and protect, as much as possible, all the elements located at the rear, and limit intrusions into the passenger compartment.

[0005] Also, the overhang of motor vehicles, i.e. the distance extending from the two wheels to the front of the vehicle, tends to be reduced in order to make vehicles more compact but also to free up more space, required by new forms of motorization, hybrid or all electric.

[0006] As a result, there is less and less space at the front of vehicles to implement compressible structures that absorb sufficient energy during frontal impacts.

[0007] Also, a problem which arises and which the present invention aims to solve is to provide a front cradle which makes it possible to reduce the front overhang of motor vehicles, without compromising the deformability of the front of the vehicles and the safety of the occupants and essential parts.

[0008] In order to solve this problem, a front cradle is proposed, adapted to be installed at the front of a motor vehicle as an extension of a chassis structural element, extending under an engine compartment of said motor vehicle to a front end of said vehicle. Said front cradle comprises:

[0009] - a rear cross member adapted to extend transversely into said motor vehicle and to be connected to said chassis structure element;

[0010] - two arms attached to said rear cross member and extending longitudinally and at a distance from each other in a direction substantially perpendicular to said rear cross member, each of said two arms having an end opposite said rear cross member, the ends of said two arms being connected to said front end of said motor vehicle.

[0011] And said two arms each have a constricted area so as to be able to break at said constricted area when said front end of said vehicle strikes an obstacle and said arms undergo a shock along a longitudinal component.

[0012] Thus, a feature of the invention lies in the implementation of arms equipped with a constricted zone so as to break at said constricted zone in the event of a frontal impact. In this way, the arms can break in a predetermined area and thus make it possible to absorb a large amount of energy during a frontal impact, in particular preserving the components located behind the cradle.

[0013] Furthermore, and according to a particularly advantageous feature of the invention, the cradle comprises a front cross member connecting the ends of the two arms together. The front cross member extends substantially parallel to the rear cross member. In this way, the two arms are joined to each other at their ends, which makes the cradle more rigid and also ensures better control of axial deformation during an impact.

[0014] According to a preferred embodiment of the invention, said constricted zone divides each of said arms into a rear arm connected to said rear crossmember and a forearm extending to said arm end, said forearm extending in a step relative to said rear arm. Consequently, when the constricted zone ruptures during an impact, the forearm can then engage along the rear arm without creating disorder inside the engine compartment in directions perpendicular to the longitudinal direction.

[0015] Furthermore, according to the invention, the cradle also comprises two support uprights erected respectively on said forearms near the two constricted areas, along a component perpendicular to said rear crossmember and said forearm. The two uprights, otherwise called "horns," provide support for drive elements. They are an integral part of the cradle.

[0016] Also, preferably, said forearm extends in a step relative to said forearm along a component perpendicular to said rear crossmember and said forearm. Moreover, the forearms extend in a step on a mean plane located above the mean plane defined by the forearms. In other words, during the impact, when the constricted areas dislocate and break, the forearms then slide on the forearms while the front of the vehicle contracts axially.

[0017] Moreover, said rear cross member has a plurality of recesses delimited by ribs inclined relative to the direction of said arms. Thanks to this feature, the rear cross member can also absorb large amounts of energy by deforming and breaking. Indeed, the longitudinal, or axial, forces exerted on the arms are transmitted through the rear cross member and the inclined ribs, which allows for greater dislocation of the cross member compared to a solid cross member or to ribs extending in a longitudinal direction.

[0018] According to a preferred embodiment of the invention, said rear crossmember comprises two rear mounting lugs spaced apart from each other and each provided with two steel inserts. The two lugs extend, for example, into the rear corners of the crossmember. And thanks to the steel inserts, a better clamping effect is achieved on the chassis structural elements, which are themselves made of steel.

[0019] Furthermore, said rear crossmember includes two opposing rear lateral mounting brackets. The two brackets receive structural elements from the chassis for improved fastening. Thus, the cradle can support the motor vehicle's engine assembly.

[0020] Furthermore, said arms advantageously comprise two opposing front lateral mounting brackets. These two front lateral brackets also allow for better retention of the cradle on the chassis elements. Preferably, these two front brackets are also equipped with steel inserts.

[0021] Furthermore, the cradle is preferably cast in one piece of aluminum. In this way, it is lighter than a cradle made of steel. Consequently, the vehicle on which it is installed is itself lighter, and therefore more fuel-efficient.

[0022] Other features and advantages of the invention will become apparent from the following description of a particular embodiment of the invention, given by way of example but not limitation, with reference to the accompanying drawings in which:

[0023] [Fig.1] is a schematic perspective top view of a front cradle according to the invention in a motor vehicle;

[0024] [Fig.2] is a schematic top view of the front cradle illustrated in [Fig.1];

[0025] [Fig.3] is a schematic side view of the object in [Fig.2] along arrow III; and,

[0026] [Fig.4] is a schematic side view of the object of [Fig.2] along arrow IV.

[0027] Figure 1 shows partially, from above, the front of a motor vehicle 10, and It is inscribed in an orthogonal coordinate system X, Y, Z, in which the X axis extends along a longitudinal front-to-back direction of the motor vehicle, oriented towards the rear; the Y axis extends along a transverse direction of the vehicle, oriented from left to right with respect to a driver in a driving situation; and the Z axis extends along a vertical direction, oriented from the floor towards the roof.

[0028] Thus, a front cradle 12, the object of the invention, can be seen through the transparent interior of the front of the motor vehicle 10. The front cradle 12 extends along the lower part of the vehicle, under an engine compartment 13, from the vehicle chassis to its bumper 15 and between its two front wheels, the right front wheel 17 and the left front wheel 19. The bumper 15 corresponds to the front end of the vehicle.

[0029] The front cradle 12 includes a rear cross member 14, which extends transversely inside the vehicle in line with chassis structural elements not shown, but to which it is connected.

[0030] Also, the cradle 12 includes two arms, a right arm 16 and a left arm 18 substantially parallel to each other, extending respectively from the rear cross member 14, to two ends 20, 22.

[0031] The two ends 20, 22 of the two arms 16, 18 are connected to each other by an anterior cross member 24. The posterior cross member 14, the two arms 16, 18 and the anterior cross member 24 thus form a rigid frame.

[0032] Also, the two arms 16, 18 include extenders 26, 28 which extend beyond the two ends 20, 22 to join a crossbar of the shield 15 not shown.

[0033] Furthermore, opposite and at the rear of the cradle 12, in the example shown in [Fig. 1], electrical energy storage equipment and high-voltage connection cables are installed. They are not shown in [Fig. 1].

[0034] One objective of the invention is to be able to preserve precisely these storage equipment and these connection cables in the event of a frontal impact of the motor vehicle.

[0035] We will now detail the front cradle 12 with reference to [Fig.2], [Fig.3] and [Fig.4], which front cradle specifically allows us to preserve these components.

[0036] Thus, we find on [Fig.2], the front cradle 12 according to the invention, seen from above and forming a frame.

[0037] It is made from a single piece of cast aluminum in an alloy containing silicon and magnesium. Thanks to the magnesium, the material is more ductile.

[0038] We find on [Fig.2], the posterior cross member 14 and the two arms, right 16, left 18, which extend from it to the two ends 20, 22. And we also find the anterior cross member 24 which joins precisely these two ends 20, 22.

[0039] Reference will now be made not only to [Fig.2], but also to [Fig.3] and [Fig.4]. Thus, it will be observed on [Fig.3] and [Fig.4] showing the front cradle 12 seen from the left side and from the right side, that the left arm 18 has a left constricted area 30 and respectively a right constricted area 32 opposite each other.

[0040] These two constricted zones 30, 32 present, at the maximum of the constriction, a section located at the right-hand side of the cutting plane Pc shown in [Fig.2], lower than less than half of the average section of arms 16, 18. Advantageously, the section of the two constricted areas 30, 32 is less than one third of the average section of arms 16, 18. The advantage of this will be explained later in the description.

[0041] Also, as illustrated in [Fig.3] and [Fig.4], the left constricted area 30 divides the left arm 18 into a left forearm 34 and a left hindarm 36, and the right constricted area 32 divides the right arm 16 into a right forearm 38 and a right hindarm 40.

[0042] Furthermore, it will be observed that the two forearms, left 34 and right 38, define an anterior mean plane Pma substantially parallel to a posterior mean plane Pmp defined by the left forearms 36 and right forearms 40, but raised relative to this posterior mean plane Pmp. The anterior mean plane Pma is preferably raised by a height h greater than half the average thickness of the arms 16, 18.

[0043] In other words, the two left forearms 34 and right forearms 38 are respectively raised relative to the left forearms 36 and right forearms 40.

[0044] Also, it will be observed in [Fig.3] that the left arm 18 has a left support upright 42 erected on the left forearm 34 near the left constricted area 30. And it will also be observed in [Fig.4] that the right arm 16 has a right support upright 44 erected on the right forearm 38 near the right constricted area 32. These support uprights 42, 44 are also referred to as "horns".

[0045] We will return to [Fig.2] to describe in more detail the rear cross member 14. It forms essentially a lattice.

[0046] It has a posterior edge 46 opposite an anterior edge 47, and a left edge 48 opposite a right edge 50. Also, it has a left part 52 substantially symmetric to a right part 54 with respect to a median plane P.

[0047] Thus, the posterior cross member 14 has a left distal rib 56 extending from the anterior edge 47 to the left edge 48 and opposite it with respect to the median plane P, a right distal rib 58 extending from the anterior edge 47 to the right edge 50. These distal ribs 56, 58 are inclined with respect to the median plane P, at an angle close to 60° for example.

[0048] In addition, the posterior cross member 14 has a left intermediate rib 60 extending from the anterior edge 47 to the posterior edge 46 and opposite with respect to the median plane P, a right intermediate rib 62 extending from the anterior edge 47 to the posterior edge 46.

[0049] These intermediate ribs 60, 62 are inclined along average directions with respect to the median plane P at an angle close to 45°.

[0050] Thus, the posterior cross member 14 has, between the left distal rib 56 and the left intermediate rib 60 from which it is separated, a left distal recess 64. And opposite, with respect to the median plane P, it has, between the right distal rib 58 and the right intermediate rib 62 from which it is separated, a right distal recess 66.

[0051] In addition, the posterior cross member 14 has between the two intermediate ribs 60, 62, two cross ribs, 68, 70, crossing in the median plane Pm and extending respectively from the anterior edge 47 to the posterior edge 46.

[0052] In addition, two secondary ribs, a left 72 and a right 74, extend from the posterior edge 46 at the level of the ends of the cross ribs 70, 68, to the intermediate ribs 60, 62.

[0053] Thus, the posterior cross member 14 has a left proximal recess 76 delimited by the left intermediate rib 60, the left secondary rib 72 and the two cross ribs 68, 70, and opposite it with respect to the median plane Pm, it has a right proximal recess 78 delimited by the right intermediate rib 62, the right secondary rib 74 and the two cross ribs 68, 70.

[0054] The purpose of this rear cross member 14, meshed or lattice-like, will be explained later in the description.

[0055] Furthermore, it has two rear fixing lugs spaced apart at each end, a left rear fixing lug 80 and a right rear fixing lug 82. These rear fixing lugs 80, 82 are respectively provided with two steel metal inserts 84, 86 to make steel-to-steel tightening easier when the cradle 14 is installed on the structural elements of the chassis.

[0056] In addition, the rear cross member 14 includes two opposing rear lateral fixing brackets, a left 88 and a right 90.

[0057] And the arms also include two opposing anterior lateral fixing brackets, a left 92 and a right 94.

[0058] Thus, thanks to the front lateral mounting brackets 82, 92, the rear lateral mounting brackets 88, 90 and the rear mounting lugs 80, 82, the cradle 12 is rigidly connected to the chassis structural elements. In this way, the cradle 12 can, despite the overhang, support the vehicle's engine, in particular.

[0059] Thus, when the motor vehicle hits an obstacle head-on, the shield 15 illustrated in [Fig.1] sinks under the effect of the impact and then causes axial forces F, along the longitudinal direction X of the vehicle, on the two arms 16, 18.

[0060] If these axial forces F reach a first threshold, for example between 80 kN and 110 kN, then the two arms 16, 18 break at their constricted zone 30, 32 respectively. The fracture of the two arms 16, 18 absorbs a significant amount of energy.

[0061] Furthermore, thanks to the vertical offset of the forearms 34, 38, relative to the forearms 36, 40, after the rupture of the constricted areas 30, 32, the forearms 34, 38 have the possibility of continuing their course according to arrow G, by sliding respectively on the back arms 36, 40.

[0062] Consequently, on the one hand, the forearms 34, 38 are guided in translation by the forearms 36, 40 without significant damage to other components. Indeed, this guidance avoids, to a certain extent, radial intrusions of the forearms 34, 38.

[0063] Moreover, the friction of the forearms 34, 38 on the forearms 36, 40 also absorbs energy. In this way, the electrical energy storage equipment and the high-voltage connection cables located behind the rear crossmember 14 are protected.

[0064] However, if the axial forces F are greater than 110 kN, then the rear cross member 14 will be able to partially dismember itself to absorb additional amounts of energy which will allow the preservation of the electrical energy storage equipment and the high voltage connection cables.

[0065] Thus, with regard to [Fig.2], considering that the two arms 16, 18 have been broken at the cutting plane Pc, the additional forces exerted longitudinally on the rear arms 36, 40 will be able to cause the partial rupture of the elements of the rear cross member 14.

[0066] Furthermore, thanks to the inclination of the distal ribs 56, 58 and intermediate ribs 60, 62 in particular, by forming polygons with the other ribs, the forces exerted on the rear cross member 14 tend to dissipate the fragments laterally rather than axially. This again helps to protect electrical equipment located behind the cross member 14.

[0067] For example, for a given amount of additional stress, the left 52 and right 54 parts of the posterior cross member 14 can break respectively along the fracture planes Prg and Prd. The left fracture plane Prg opens into the left edge 48 and the left distal recess 64, while the right fracture plane Prd opens into the right edge 50 and the right distal recess 66.

[0068] This rupture allows additional energy to be absorbed without causing an excursion towards the electrical equipment.

[0069] It is understood from the view of the rear cross member 14 in [Fig.2], that other break zones of the rear cross member 14 in lattice are possible and allow to absorb still other quantities of energy.

[0070] Although the invention has been described in connection with a particular embodiment, it is by no means limited to it and includes all technical equivalents of the means described, as well as combinations thereof, if these fall within the scope of the invention. For example, the ribs of the rear cross member 14 can be arranged differently to provide a similar result.

[0071] Furthermore, the use of the verb "to include", "to understand" or "to include" does not exclude the presence of other elements or steps than those stated in a claim.

Claims

Demands

1. Front cradle (12) adapted to be installed at the front of a motor vehicle in line with a chassis structural element extending under an engine compartment (13) of said motor vehicle to a front end of said vehicle, said front cradle (12) comprising: - a rear cross member (14) adapted to extend transversely in said motor vehicle and to be connected to said chassis structural element; - two arms (16, 18) integral with said rear cross member (14) and extending longitudinally and at a distance from each other in a direction substantially perpendicular to said rear cross member, each of said two arms (16, 18) having an end (20, 22) opposite said rear cross member (14), the ends of said two arms being connected to said front end of said motor vehicle;characterized in that said two arms (16, 18) each have a constricted area (32, 30) so that they can break at said constricted area when said front end of said vehicle strikes an obstacle and said arms (16, 18) are subjected to an impact along a longitudinal component.

2. Front cradle according to claim 1, characterized in that it further comprises a front cross member (24) connecting said ends (20, 22) of said two arms (16, 18) together.

3. Front cradle according to claim 1 or 2, characterized in that said constricted zone (30, 32) divides each of said arms (16, 18) into a rear arm (36, 40) connected to said rear cross member (14) and a forearm (34, 38) extending to said end (22, 20) of arm, said forearm (34, 38) extending in step out from said rear arm (36, 40).

4. Front cradle according to claim 3, characterized in that it further comprises two support uprights (42, 44) erected respectively on said forearms (34, 36) near the two constricted areas (30, 32), along a component perpendicular to said rear cross member (14) and said forearm.

5. Front cradle according to claim 3 or 4, characterized in that said forearm (34, 38) extends in a step relative to said forearm (36, 40) along a component perpendicular to said posterior cross member (14) and said forearm.

6. Front cradle according to any one of claims 1 to 5, characterized in that said rear cross member (14) has a plurality of recesses (64, 76; 78, 66) delimited by ribs (56, 60, 72, 68, 70, 62, 74, 58) inclined with respect to the direction of said arms (16, 18).

7. Front cradle according to any one of claims 1 to 6, characterized in that said rear cross member (14) comprises two rear fixing lugs (80, 82) spaced apart from each other and respectively provided with two steel inserts (84, 86).

8. Front cradle according to any one of claims 1 to 7, characterized in that said rear cross member (14) comprises two rear lateral fixing brackets (88, 90) opposed to each other.

9. Front cradle according to any one of claims 1 to 8, characterized in that said arms (16, 18) comprise two opposing front lateral fixing brackets (94, 92).

10. Front cradle according to any one of claims 1 to 9, characterized in that it is cast in one piece of aluminum.

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