VEHICLE HAVING A STRUCTURE HAVING A THIRD LOAD PATH BETWEEN AN ENGINE MOUNT AND A FRONT SIDE RAIL, AND METHOD FOR ASSEMBLING SUCH A VEHICLE

Description

[0001] The present invention claims priority from French application 2001979 filed on February 27, 2020.

[0002] The invention relates to the front structure of a motor vehicle, vehicles showing such a structure and methods of manufacturing such vehicles.

[0003] To address current environmental challenges, car manufacturers are increasingly offering vehicles with different powertrains, such as traditional combustion engine engines and electric or hybrid powertrains. Vehicles with hybrid and electric powertrains have seen their weight increase considerably compared to their combustion engine versions due to the presence of propulsion batteries. This increase in weight can be around 300 to 400 kg for a vehicle, for example. Because of this weight difference, body structures designed for combustion engine vehicles cannot be used to produce vehicles with the same silhouette with a hybrid or electric powertrain without degrading the safety features offered by the vehicle.In fact, the energy to be absorbed in the event of a frontal impact becomes greater due to the increase in mass.

[0004] It is known to reinforce the front structure of a motor vehicle by means of reinforcement pieces or tie rods.

[0005] Thus, for example, document FR2937943 describes a motor vehicle structure comprising a chassis with two side members connected by a cross member; a pair of arms, each arm having a first end mounted on the front portion of a side member and a free end; and a body. The structure further comprises a reinforcing piece which connects the free ends of said arms to said cross member, to increase the rigidity of said structure; an underbody element; and complementary reinforcing means which comprise, on each side of said underbody element, a front tie rod which has a first end fixed to said reinforcing piece and a second end fixed to said underbody element. The proposed structure tends to compensate for a lack of rigidity of the front structure observed in the absence of a roof for convertible type vehicles.This structure therefore does not offer a solution to the problems of deformation which may arise due to an increase in the mass of the vehicle due to the installation of propulsion batteries.

[0006] Document FR2902401 describes a flexible sheet metal cradle tie rod intended to connect the end of a cradle for a motor vehicle axle to the body of said vehicle. The tie rod is formed of a longitudinal blade having a twist around its longitudinal axis so that a first part of the blade projected in a plane perpendicular to the longitudinal axis of the blade forms a given angle with a projection in the same plane of a second part of the blade. The tie rod described makes it possible to avoid the use of an elastic articulation between the tie rod and the cradle. The tie rod described does not make it possible to compensate for an increase in the mass of the vehicle due to the installation of propulsion batteries.

[0007] Document FR2859157 describes a structure of a front part of a motor vehicle, comprising on the one hand an upper part formed of at least two side members which extend longitudinally in front of the passenger compartment of the vehicle and which are connected in their front end part by a cross member, and on the other hand a lower part formed of at least one frame cradle which supports functional elements of the vehicle, which is formed of at least two longitudinal arms extending towards the front of the vehicle, and which is connected to the side members of the upper part by vertical tie rods. The structure further comprises energy absorbers, which are fixed on the frame cradle towards the front of the vehicle, and the main dimension of these energy absorbers is longitudinal, such that in the event of a frontal impact, these energy absorbers absorb sufficient energy to minimize the deformation of the frame cradle. The proposed structure does not solve the problem posed.

[0008] Document FR2813269 describes a motor vehicle body structure assembly, of the type which comprises, from front to rear, a body structure element which forms in particular a support for mechanical components of the vehicle, and a rigid cell forming the passenger compartment of the motor vehicle. The body structure element comprises, in a first upper horizontal plane, at least two upper longitudinal side members which extend forward from the cell and, in a second lower horizontal plane, two lower longitudinal side members which extend parallel below the upper side members and whose intermediate parts are each connected to the associated upper side member by at least one tie rod. The assembly comprises protective side fairings which are carried by the tie rods. The proposed structure does not solve the problem posed.

[0009] Documents EP3590792, FR2798109 and FR2928127 disclose a vehicle comprising a cradle fixed at the rear extension level to a stretcher directly or via a tie rod.

[0010] The invention aims to provide a solution to at least one of the drawbacks and problems encountered in the prior art. In particular, the invention proposes to solve the problems linked to the increase in forces during a frontal impact for vehicles showing an increased mass; for example, due to the presence of a motorization involving the presence of propulsion batteries.

[0011] For this purpose, and according to a first aspect, the invention relates to a vehicle comprising a pair of front stretchers and a cradle, the cradle comprising a body and rear extensions, the vehicle is remarkable in that at least one rear extension of the cradle is fixed to a stretcher by means of at least one tie rod. At least one rear extension of the cradle being fixed to a front stretcher by means of at least one tie rod, the vehicle further comprising at least one rear cradle fixing bracket and at least one rear cradle fixing bracket reinforcement, the vehicle is remarkable in that at least one rear extension of the cradle is fixed to a rear cradle fixing bracket, to a rear cradle fixing bracket reinforcement and to a tie rod by a common fixing screw.

[0012] It goes without saying that the cradle is the front cradle of the vehicle.

[0013] As will be understood from reading the definition just given, the invention proposes to stabilize the front structure in the event of a frontal impact by providing a new path for transmitting forces between the cradle and the front side members passing through the rear extensions of the cradle. Indeed, it has been observed that in the event of a frontal impact scenario, the cradle of vehicles with hybrid or electric engines tends to deform due to the increase in mass linked to the installation of the propulsion batteries. Research has shown that the cradle fasteners could play a role in these deformation phenomena and tend to be skewed under the force. The deformations could cause tearing of the sheets and therefore a loss of a force path for retaining the engine. In such a situation, the risks of intrusion of the engine into the passenger compartment are increased, which is unacceptable.The invention is remarkable in that by connecting the rear extensions of the cradle to the front stretcher, it offers a new path for transmitting forces compared to the already existing paths, namely the front attachments of the cradle to the front stretcher and the attachments of the cradle to the rear attachment support of the cradle. The distribution of forces between the three force paths will reduce the stresses on the attachments and resolves at least in part the deformation problems observed.

[0014] According to embodiments, at least one rear extension of the cradle being fixed to a front stretcher by means of at least one tie rod, the vehicle is remarkable in that said or at least one of said tie rods is fixed to a rear extension and / or to a front stretcher by screwing.

[0015] According to embodiments, at least one rear extension of the cradle is attached to a front stretcher by means of at least one tie rod, and the vehicle is remarkable in that at least one tie rod is a rectilinear part in the form of a profile or a hollow body. Preferably, at least one tie rod is in the form of a rectilinear profile showing at least one consolidation edge.

[0016] According to embodiments, at least one rear extension of the cradle being fixed to a front stretcher by means of at least one tie rod, the vehicle is remarkable in that the or at least one of the tie rods is made of a high elastic limit steel and / or the or at least one of the tie rods is made of a sheet metal having a thickness of at least 2 mm and / or the or at least one of the tie rods has at least one stiffening rib extending along at least a portion of its length and / or the or at least one of the tie rods is inclined so that one of its ends is arranged higher than the other end.

[0017] According to embodiments, at least one front stretcher is a piece joined together so as to show a front portion and a rear portion, the rear portion showing a mechanical strength greater than the mechanical strength of the front portion, and at least one rear extension of the cradle is fixed to the rear portion of said front stretcher directly or by means of at least one tie rod. Preferably, the rear and front portions are formed from two different grades of steel.

[0018] According to embodiments, the front stretchers showing a rear end, the vehicle is remarkable in that it is a hybrid or electric motorized vehicle comprising at least one propulsion battery; in that the vehicle comprises at least one side-spar connecting piece fixed to the front stretcher and a cross member fixed to the rear end of said front stretcher, and at least one rear extension of the cradle is fixed to a front stretcher directly or by means of at least one tie rod at a location situated between the side-spar connecting piece and a fixing interface intended for fixing the front stretcher to said cross member.

[0019] According to embodiments, the vehicle is a thermally powered vehicle comprising a thermal engine, or an electrically powered vehicle comprising at least one propulsion battery, or a hybrid powered vehicle comprising a thermal engine and at least one propulsion battery. Preferably, the vehicle is a hybrid powered vehicle comprising a thermal engine and at least one propulsion battery or an electrically powered vehicle comprising at least one propulsion battery. The implementation of the invention is particularly advantageous in the case of hybrid and / or electric powered vehicles, it is nevertheless applicable to thermal powered vehicles so as to further increase their safety performance.

[0020] According to a second aspect, the invention relates to a method of mounting a vehicle according to the first aspect, the method being remarkable in that it comprises a step of fixing at least one rear extension of the cradle to a front stretcher by means of at least one tie rod; preferably, said fixing step is carried out by screwing.

[0021] The invention will be well understood and other aspects and advantages will appear clearly on reading the following description given with reference to the appended figures in which: [ Fig. 1 ] There figure 1 is a bottom view of structural elements of a vehicle according to the invention [ Fig. 2 ] There figure 2 is a perspective view of a tie rod according to the invention.

[0022] In the following description, the term "comprise" is synonymous with "include" and is not limiting in that it allows the presence of other elements in the vehicle or other steps in the method to which it relates. It is understood that the term "comprise" includes the terms "consist of". The terms "top" and "bottom" will be understood in their general sense, the term "bottom" designating a greater proximity to the ground. In the different figures, the same references designate identical or similar elements.

[0023] We will first refer to the figure 1 showing a partial view of a body structure of a vehicle according to the invention, as seen from below, i.e. from the ground. In the illustrated embodiment, the vehicle is a hybrid motor vehicle comprising a thermal engine and at least one propulsion battery. Those skilled in the art will nevertheless be able to adapt the invention to thermal motor vehicles comprising a thermal engine or to electric motor vehicles comprising at least one propulsion battery.

[0024] The body structure comprises a cradle 1 showing a body 3 and a pair of rear extensions 5. The structure also comprises a pair of front stretchers 7 to which the cradle 1 is fixed. The front portion of the body 3 of the cradle 1 is fixed to the front stretchers 7 by means of front fixing pieces 9. The rear portion of the body 3 of the cradle 1 is fixed to the underbody by means of rear cradle fixing brackets 11. The rear cradle fixing brackets 11 are themselves assembled to the front stretcher 7. The rear cradle fixing brackets 11 are arranged and dimensioned to leave a passage 13 between them, intended to receive the tunnel (not shown). The cradle 1 is also fixed by its rear extensions 5 to said rear cradle fixing brackets 11 and to rear cradle fixing support reinforcements 15 not shown and assembled inside the rear cradle fixing brackets.

[0025] The vehicle is remarkable in that at least one rear extension 5 of the cradle is further attached directly or by means of at least one tie rod 17 to the front stretchers.

[0026] In an embodiment not shown, at least one rear extension of the cradle is attached directly to the front stretchers. To do this, the rear extension(s) have a greater length than in usual configurations so as to extend to the front stretcher which is located on the same side. It is understood that in such a case, at least one rear extension is configured to extend towards the rear of the vehicle so as to form a non-right angle with the longitudinal axis of the vehicle. Advantageously, at least one rear extension has at least two attachment interfaces distributed along its length; namely, a first attachment interface intended for its attachment to the rear cradle attachment support or to the assembly formed by a rear cradle attachment support and a cradle attachment support reinforcement, and a second attachment interface intended for its attachment to a front stretcher.The rear cradle extension(s) showing two ends, namely an anchor end connected to the cradle body and a terminal free end, the second attachment interface is arranged at the terminal end of the rear cradle extension(s).

[0027] In the embodiment shown in figure 1 , the cradle 1 shows rear extensions 5 of usual size, that is to say that they do not extend to the front stretcher 7 which is located on the same side. Their attachment to the front stretcher 7 is done indirectly by means of tie rods 17. This embodiment offers the advantage of being able to use the same cradle 1 for the different versions of the vehicle. The cradle intended for the version of the vehicle showing a thermal engine being then the same as that intended for the version of the vehicle showing a hybrid or electric engine, it is possible to achieve economies of scale. The invention is remarkable in that it makes it possible to adapt an architecture already existing for vehicles with thermal engines to vehicles with hybrid or electric engines.

[0028] The tie rod 17 is a straight piece showing two ends. It is fixed to a rear extension 5 by its front end and to a front stretcher 7 by its rear end. According to a preferred embodiment it is fixed to a rear extension 5 and / or to a front stretcher 7 by screwing. The screwing is done at the time of vehicle assembly. However, a person skilled in the art will benefit from the tie rod being pre-assembled with the cradle 1 at the time of the styling operation.

[0029] Advantageously, a person skilled in the art will be able to take advantage of the fixing interfaces already existing between the rear extensions 5 of the cradle and the rear cradle fixing supports 11 or the assembly formed by the rear cradle fixing supports 11 and the cradle fixing support reinforcements 15. Thus, in one implementation of the invention, at least one rear extension 5 is fixed to a rear cradle fixing support 11 and to a tie rod 17 by a common fixing screw. Preferably, at least one rear extension 5 is fixed to a rear cradle fixing support 11, a cradle fixing support reinforcement 15 and a tie rod 17 by a common fixing screw. This configuration makes it possible to limit the number of screws and associated screwing operations.

[0030] Advantageously, the tie rod 17 (or where appropriate the terminal end of a rear subframe extension) is fixed to the front stretcher 7 at its rear portion arranged under the floor of the vehicle. In vehicles with hybrid or electric engines, the front stretchers 7 are shortened compared to the front stretchers shown by vehicles with thermal engines. Whatever the engine chosen for the vehicle, the person skilled in the art will benefit from at least one front stretcher 7 being a butted part showing a front portion 19 and a rear portion 21. It is recalled, if necessary, that the butted parts comprise two parts assembled end to end. It is therefore possible to use sheets showing different steel grades and / or different thicknesses when manufacturing a front stretcher 7.

[0031] Advantageously, the rear portion 21 of at least one front stretcher 7 exhibits a mechanical strength greater than the mechanical strength exhibited by the front portion 19 of the same front stretcher 7. Preferably, the rear portions 21 and front 19 are formed from two different grades of steel. Thus, the cradle 1 is connected by its rear extensions either directly or by means of at least one tie rod 17 to the portion exhibiting the greatest mechanical strength, namely to the rear portion 21 of said front stretcher 7.

[0032] For example, the rear portion 21 of the front stretcher 7 is made of a steel selected from high yield strength (HLE) steels, very high yield strength (THLE) steels or ultra high yield strength (UHLE) steels. These steels have a fine-grained structure and exhibit excellent mechanical characteristics (yield strength, fatigue strength and resilience) as well as good formability.

[0033] For the record, mild steels have a yield strength ranging from 300 to 350 MPa, high strength (HSL) steels have a yield strength ranging from 400 to 700 MPa, very high strength (VHSL) steels have a yield strength ranging from 800 to 1000 MPa and ultra high strength (UHSL) steels have a yield strength of 1100 to 1500 MPa. Yield strength is measured according to ISO 6892-1:2016.

[0034] Advantageously, the body structure of the vehicle also comprises side members (not shown) and side member-side member connecting pieces 23. Said side member-side member connecting pieces 23 are for example fixed to the front side members 7 by welding.

[0035] When the vehicle is a hybrid or electric motor vehicle comprising at least one propulsion battery, the battery or batteries may be attached to the rear ends of the front stretchers 7. For example, the rear end of the front stretcher 7 is attached to a cross member (not shown) on which is mounted a podium carrying at least one frame in which at least one propulsion battery is arranged. For this purpose, the rear end of the front stretchers 7 shows an attachment interface 25 to the cross member. This attachment interface 25 comprises for example a hole with a welded nut for screwing said front stretchers 7 to said cross member.

[0036] According to preferred embodiments of the invention, the tie rod 17 (or where appropriate the terminal end of a rear cradle extension) is fixed to the front stretcher at a location situated between the stretcher-side member connecting piece 23 and the fixing interface 25 intended for fixing the front stretcher 7 to the cross member carrying the propulsion batteries.

[0037] According to preferred embodiments, at least one rear extension 5 of the cradle is fixed to a front stretcher 7 by means of at least one tie rod 17. Advantageously, the tie rod 17 is a rectilinear part in the form of a profile or a hollow body extending in a direction forming a non-right angle with the longitudinal direction of the vehicle. The tie rod is oriented in the front-to-rear direction towards the outside of the vehicle. It is advantageously inclined relative to the horizontal so that one of its ends is arranged higher than the other end. An exemplary embodiment of a tie rod 17 according to the invention is illustrated in figure 2 .

[0038] The tie rod 17 advantageously has a height as low as possible so as not to degrade the ground clearance performance of the vehicle. For example, it has a height of less than 2.0 cm, preferably less than 1.5 cm, more preferably less than 1.2 cm. For example, it has a height of between 0.2 and 2.0 cm, preferably between 0.3 and 1.2 cm, more preferably between 0.5 and 1.0 cm. It has a length of less than 50 cm, for example between 20 and 40 cm.

[0039] When it is in the form of a profile, the tie rod 17 can be obtained by stamping and advantageously shows an omega shape with at least one consolidation edge; preferably at least one consolidation edge shows a notch 29 for the passage of a bundle of electric wires. When it is in the form of a hollow body, such as a tube, its ends are advantageously crushed.

[0040] Preferably, the tie rod 17 is made of steel, the steel is preferably selected from high yield strength (HLE) steels, very high yield strength (THLE) steels or ultra high yield strength (UHLE) steels. For example, the tie rod 17 is made of high yield strength steel.

[0041] According to embodiments, at least one tie rod 17 is made from a sheet metal having a thickness of at least 2 mm; for example at least 2.5 mm. The thickness will be chosen according to the desired mechanical performance.

[0042] According to embodiments at least one tie rod 17 has at least one stiffening rib extending along its length. Those skilled in the art may consider reinforcing the rigidity of the tie rod by other means such as for example by lengthening the consolidation edges when they are present or by adding a gusset.

[0043] The invention also relates to a method of manufacturing a vehicle as defined above, comprising a step of fixing at least one rear extension 5 of the cradle to a front stretcher 7 either directly or by means of at least one tie rod 17. Said fixing step is preferably carried out by screwing.

Claims

1. Vehicle comprising a pair of front side brackets (7) and a cradle (1), the cradle (1) comprising a body (3) and rear extensions (5), at least a rear extension (5) of the cradle being fixed to a front stretcher (7) by at least one tie rod (17), characterised in that the vehicle comprises in addition, at least one cradle-rear attachment bracket (11) and at least one cradle-rear attachment bracket reinforcement (15), the vehicle is characterised in that at least one rear extension (5) of the cradle is attached to a cradle-rear attachment bracket (11) and to a cradle-rear attachment bracket reinforcement (15) and to a tie rod (17) by a common fixing screw.

2. The vehicle as claimed in claim 1, wherein said at least one of said tie rods (17) is fixed to a rear extension (5) and / or to a front stretcher (7) by screwing.

3. Vehicle according to one of Claims 1 to 2, in which at least one rear extension (5) of the cradle is fixed to a front side-piece (7) by means of at least one tie-rod (17), the vehicle is characterised in that at least one tie-rod (17) is a rectilinear component in the form of a section or a hollow body; preferably at least one tie rod is in the form of a section straight line showing at least one consolidation edge.

4. Vehicle according to one of Claims 1 to 3, in which at least a rear extension (5) of the cradle being fixed to a front stretcher (7) by the vehicle is characterised in that the or at least one of the tie rods (17) consists of a high elastic limit steel and / or the or at least one of the tie rods (17) is realised in a sheet having a thickness of at least 2 mm.

5. Vehicle according to one of Claims 1 to 4, in which at least since a rear extension (5) of the cradle is fixed to a front stretcher (7) by means of at least one tie rod (17), the vehicle is characterised in that the or at least one of the tie rods (17) is inclined so that one of its ends is arranged above the other end; and / or in that the or at least one of the tie rods (17) show at least one stiffening rib extending along at least a portion of its length.

6. Vehicle according to one of Claims 1 to 5, the front stretchers (7) showing a rear end, the vehicle is characterised in that it is a vehicle hybrid or electric motor comprising at least one battery of propulsion; and / or in that the vehicle comprises at least one connecting component (23) side-rail fastened to the front side-rail (7) and a cross-member fastened to the rear end of said front side-rail, and at least one rear extension (5) of the cradle is fastened to a front side-rail (7) directly or via at least one tie rod (17) at a location between the connecting component (23) side rail and a fastening interface (25) for fastening the front strut (7) to said cross-member.

7. Vehicle according to one of Claims 1 to 6, characterised in that at least one front stretcher (7) is a component which is butt-jointed so as to show a part front part (19) and a rear part (21), the rear part (21) showing a resistance mechanical strength greater than the mechanical strength of the front part (19), and at least one rear extension (5) of the cradle is fixed to the rear part (21) of said front side brace (7) directly or via at least one tie rod (17); preferably, the rear part (21) and the front part (19) are made of two steel grades different.

8. A method of assembly line a vehicle according to any one of claims 1 to 7, comprising a step of fixing at least one rear extension (5) of the cradle to a front stretcher (7) by means of at least one tie rod (17); preferably, said fixing step is carried out by screwing.