Rockers for vehicles and vehicles comprising such rockers

A rocker (2) of a vehicle, the vehicle and the rocker (2) comprising a main elongation axis, a width axis (Y) and a height axis (Z), a lower portion and an upper portion, the rocker (2) further comprising a central core (3) comprising a length along the main elongation axis and a height along the height axis (Z); two hollow units (4, 5) extending along the length and on one side and the other of the central core (3), such that one of the units (4) is closer to the outside of the vehicle (1) than the other unit (5), and a cross-section of the units in the main elongation axis, forms a closed polygon on the length of the central core (3); and two flanges (6) projecting from the lower and upper portions of the rocker (2).

This application is a National Stage Application of PCT/EP2016/055705 filed on Mar. 16, 2016, which claims the benefit of French Patent Application n° 1552203 filed on Mar. 17, 2015 and which application are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications.

The present disclosure relates to the field of structural parts involved in making vehicle frames, specifically rockers of a vehicle bodywork, as well as vehicles comprising such rockers.

BACKGROUND

The bending strength performances are essential for the side structures of the central underbody of vehicles (“rocker” according to well-known English terminology) in order to ensure the vehicle passengers are protected in the event of side impacts that cause the rockers to bend.

Nevertheless, none of these documents discloses vehicle underbody structures enabling a satisfactory compromise between bending strength and mass reduction.

There is a need in the market to lower the mass of vehicle frames to an even greater extent in order to reduce fuel consumption, without reducing the mechanical performance of the frame.

The object of the present disclosure is to provide rockers, as well as vehicles comprising such rockers, which improve mechanical performances in terms of bending strength in order to ensure protection for the passengers of a vehicle, whilst having minimum mass to, in particular, ensure optimal performance of the vehicle in terms of fuel consumption.

SUMMARY

The aforementioned aim is achieved according to claim1.

In a first aspect a vehicle comprising a rocker is provided. The vehicle and the rocker comprise a main elongation axis, a width axis and a height axis, a lower portion and an upper portion. The rocker also comprises a central core comprising a length extending along the main elongation axis and a height extending along the height axis and two hollow units extending along the length of the central core and arranged on one side and the other of the central core such that one of the units is closer to an outside of the vehicle than the other unit and such that a cross-section of the units, in the main elongation axis (X), forms a closed polygon on the length of the central core. The rocker further comprises two flanges projecting from the lower portion and the upper portion of the rocker, wherein the units comprise a height extending along the height axis, and the sum of the height of the two units is not more than the height of the central core that separates the two flanges. The rocker is adapted such that, when it is subjected to bending created by application of a force directed along the width axis or the height axis, it comprises a neutral elongation axis situated between the two units and which delimit a first area of the rocker that is subjected to tension and a second region of the rocker that is subjected to compression. At least 80% of one of the units is situated in the first area and at least 80% of the other unit is situated in the second area. And the unit that is arranged closest to the outside of the vehicle is situated closer to the upper portion of the vehicle than the other unit.

According to this aspect, the fact that a vehicle comprises such a rocker, in particular the fact that a unit that is arranged closest to the outside of the vehicle is situated closer to the upper portion of the vehicle than the other unit, in combination with the other features of the units, enables the maximum bending strength and the energy absorbed to be increased when the rocker is deformed compared to the known structures, with an identical mass. It also enables the penetration of an object colliding laterally against the vehicle to be limited. Moreover, such a rocker is particularly adapted for the bending strength and energy absorption thereof to be maximal in the event that bending is created by the application of a force directed along the width of the vehicle, from the outside towards the inside of the vehicle (typically the lateral collision with another vehicle).

In some examples, the disclosure may further be complemented by the following technical features that may be either taken alone or in any of the possible technical combinations thereof.

In some examples, each unit may comprise a wall that may be transversal to the length of the central core. The wall may be inclined at an angle comprised between 90° and 105° with respect to the height axis.

In some examples, each unit may be formed by assembling reinforcements with the central core. In some of these cases, the reinforcements assembled with the central core may have an elastic limit greater than that of the central core.

In some examples, the rocker may be formed by the assembly of two lateral reinforcements so as to form the central core, the two units and the flanges.

In some examples, the central core may comprise reinforcements so as to be more stiffened. In some of these cases, the central core may comprise a lateral rib situated opposite each of the units along the width axis, the lateral rib may be directed such that it projects opposite the unit.

In some examples, the whole of one unit may be situated in the first area and the whole of the other unit may be situated in the second area.

In some examples, the units may be identical in shape. In others, the units may be different in shape. In more examples, the units may comprise steps or levels.

In a further aspect, the disclosure relates to a rocker of a vehicle substantially as hereinbefore described. The rocker comprises a central core comprising a length extending along the main elongation axis and a height extending along the height axis. The rocker further comprises two hollow units extending along the length of the central core and arranged on one side and the other of the central core such that one unit is closer to the outside of the vehicle than the other unit, and such that a cross-section of the units, in the main elongation axis, forms a closed polygon on the length of the central core. And the rocker further comprises two flanges projecting from the lower portion and the upper portion of the rocker.

DETAILED DESCRIPTION OF EXAMPLES

As shown inFIGS. 1 and 2, a vehicle1according to the present disclosure may comprise:a main elongation axis X along which the length of the vehicle1may extend;a width axis Y along which the width of the vehicle1may extend;a height axis Z along which the height of the vehicle1may extend.

The vehicle1may also comprise two rockers2, which may be situated underneath the doors of the vehicle1. The rockers2may comprise a length extending along the main elongation axis X, a width extending along the width axis Y, and a height extending along the height axis Z.

The vehicle1may also comprise an upper portion and a lower portion. In a normal working position, the vehicle1may comprise a roof arranged on the upper portion of the vehicle1, and the rockers2may be situated in the lower portion of the vehicle1.

The rockers2may further comprise a lower portion101and an upper portion102. When the vehicle1is in a normal working position, the lower portion101of the rockers2may be oriented towards the ground, whilst the upper portion102of the rockers2may be oriented towards the roof of the vehicle1.

As shown inFIGS. 3aand 3b, the rocker2may comprise:a central core3that may comprise a length extending along the main elongation axis X, a width extending along the width axis Y, and a height extending along the height axis Z;two hollow units4and5that may extend along the length of the central core3and may be arranged on one side103and the other104of the central core3such that unit4may be closer to the outside of the vehicle1than unit5, and such that a cross-section of the units4,5in the main elongation axis X may form a closed polygon on the length of the central core. The units may comprise a length extending along the main elongation axis X, a width extending along the width axis Y, and a height extending along the height axis Z; andtwo flanges6,6′ that may project from the lower portion101and from the upper portion102of the rocker2, such that the rocker2may be assembled with other elements of the bodywork of the vehicle1

The sum of the height of the two units4and5may be not more than the height of the central core3that separates the two flanges6,6′ such that the units4and5do not overlap along the height axis Z.

The unit4that may be arranged closest to the outside of the vehicle1may be situated closer to the upper portion of the vehicle than the unit5.

Each unit4and5may be formed by several walls. More specifically, each unit4and5may comprise:at least one upper wall41,42,51,52, which may be a wall transversal to the central core3and to the height axis Z and which may form part of the unit4or5closest to the upper portion of the vehicle1;at least one lower wall43,44,53,54, which may be a wall transversal to the central core3and to the height axis Z and which may form part of the unit4or5closest to the lower portion of the vehicle1;at least one outer lateral wall45,55, which may be a wall that links the upper42,52and lower43,53walls and which may form part of the unit4or5closest to the outside of the vehicle1. Alternatively, the outer lateral wall45,55may be parallel to the central core3, and/or to the height axis Z; andat least one inner lateral wall46,56, which may be a wall that links the upper42,52and lower44,54walls and which may form part of the unit4or5closest to the inside of the vehicle1. Alternatively, the outer lateral wall46,56may be parallel to the central core3, and/or to the height axis Z and/or to the outer lateral wall45,55.

In more examples, the units4and5may each form a quadrilateral, for example any trapezoid. In yet more examples, such as the one shown inFIGS. 3aand 3b, the units4and5may each form a hexahedron. The hexahedron may have two parallel sides.

The polygons formed by the cross-section of the units4and5along the main elongation axis X shown inFIGS. 3aand 3bmay have angled apexes. However, the units4and5of the present disclosure are not limited to this example, and the cross-section thereof along the main elongation axis X may form polygons where the apexes between the faces are rounded. Indeed, in circumstances regarding stress concentration or manufacturing constraints, it may be desirable to form rounded apexes.

When the rocker2is subjected to a force F directed along the width axis Y, and oriented from the outside towards the inside of the vehicle1, the rocker2may bend towards the inside of the vehicle1. During this bending, the rocker2may be divided into two different areas separated by a neutral elongation axis ψ situated between the two units4and5, and which may be perpendicular to the force F. A first area may be subjected to compression, whilst a second area may be subjected to tension.

The neutral elongation axis ψ may be situated between the units4and5such that at least 80% of the unit4may be situated in the first area110and may work in compression, and at least 80% of the unit5may situated in the second area112and may work in tension.

When the rocker is subjected to a force F′ extending along the height axis Z, and oriented from the lower portion towards the upper portion of the vehicle1, the rocker2may bend towards the upper portion of the vehicle1. During this bending, the rocker may be divided into two different areas separated by a neutral elongation axis ψ′ situated between the two units4and5, and which may be perpendicular to the force F′. A first area116may be subjected to compression, whilst a second area118may be subjected to tension.

The neutral elongation axis ψ′ may be situated between the units4and5, such that at least 80% of the unit4may be situated in the first area and may work in compression, and at least 80% of the unit5may be situated in the second area and may work in tension.

In examples, for bending created by the application of a force directed along the height axis Z, the units4and5may only be situated in a single area, such that a unit4or5may only work in compression whilst the other unit may only work in tension.

When the vehicle1is in use, the rockers2may mainly be subjected to bending created by the application of forces directed along the width axis Y and the height axis Z, and mostly along the width axis Y. Thus, the fact that for these mechanical stresses, at least 80% of a unit4or5may work in compression whilst at least 80% of the other unit may work in tension enables an optimal compromise to be obtained between maximum strength of the rockers2, energy absorption, mass and volume of the rockers2.

Indeed, the applicant has found that if the two units both work in compression or in tension, the rocker collapses more quickly than when one unit works in compression whilst the other works in tension.

It is thus possible to manufacture a rocker that has maximum bending strength and energy absorption during the upper deformation thereof of a rocker of the state of the art, whilst having an identical mass.

Moreover, as shown inFIGS. 4aand 4b, the fact that the unit4, is arranged closest to the outside of the vehicle1and is situated closer to the upper portion of the vehicle1than the unit5, enables the penetration of a second vehicle9colliding against the side of the vehicle, at the height of a door D, to be limited.

Indeed, under the effect of the force applied by the second vehicle9, and more specifically by the bumpers90of said second vehicle9, the door D of the vehicle1may be pushed towards the inside of the vehicle1. Since the unit4may be situated towards the outside and the upper portion of the vehicle1, the door, during the deformation thereof towards the inside of the vehicle, may be limited in its deformation by unit4. Such a limitation of the movement of the door D towards the inside of the vehicle1enables the inwards penetration of said vehicle1to be limited, which is an important security factor.

As shown inFIGS. 4cand 4d, if the unit4was not in this position, for example, being situated closer to the inside of the vehicle, the penetration of the door towards the inside of the vehicle would be greater since the door would be limited in the deformation thereof towards the inside of the vehicle1only later. Indeed, as may be seen inFIG. 4d, there is a gap E between the distance at which the second vehicle9starts to be limited in the penetration thereof, and more specifically the bumpers90, when the unit4is situated towards the outside and the upper portion of the vehicle1, and when it is not.

The upper portion of the rockers2of a vehicle1may indeed be situated, in most cases, at the same level as the bumpers90of the second vehicle9(this effectively varies depending on the model of the vehicle1and the second vehicle9).

The rocker2may be manufactured according to at least two possible variants. In a first manufacturing variant, as shown inFIG. 5, the rocker2may be manufactured by assembling two lateral reinforcements P1and P2. The two reinforcements P1and P2may comprise hollow parts such that their assembly forms the central core3, the two units4and5, as well as the two flanges6,6′. In order to do so, the reinforcements P1and P2may each comprise at least one hollow part that is staggered along axis Z with respect to the hollow part of the other piece.

Alternatively, the pieces P1and P2may comprise several hollow parts, such that when the reinforcements P1and P2are assembled, the central core3is more rigid.

In a second manufacturing variant, as shown inFIG. 6, the rocker2may be manufactured by assembling at least two reinforcements R1and R2on a plate that forms the central core3and the flanges6, such that the units4and5are formed.

Alternatively, the reinforcements R1and R2may be hat-shaped reinforcements that comprise a U-shaped body and two lateral flanges, and the reinforcements R1and R2may be assembled to the plate forming the central core3through lateral flanges thereof.

Alternatively, the units4and5may each be formed by assembling two Z-shaped reinforcements.

According to a first example, as shown inFIG. 7, the units4and5may be spaced apart along the height of the central core3. Indeed, there is a central core3height between the lower wall43of unit4and the upper wall51of unit5.

The example shown inFIG. 7may be carried out according to the second manufacturing variant of the rocker2, i.e. by assembling reinforcements on a plate forming the central core3and the flanges6.

However, this example may also be carried out according to the first manufacturing variant of the rocker2, i.e. by assembling two reinforcements so as to form the central core3, the units4and5, and the flanges6.

According to a second example, as shown inFIG. 8, the units4and5may not be spaced along the height of the central core3. Indeed, there is no central core3height between the lower wall43of unit4and the upper wall51of unit5.

The example shown inFIG. 8may be carried out according to the second manufacturing variant of the rocker2, i.e. by assembling reinforcements on a plate forming the central core3and the flanges6.

However, this example may also be carried out according to the first manufacturing variant of the rocker2, i.e. by assembling two reinforcements so as to form the central core3, the units4and5, and the flanges6.

According to a third example, as shown inFIG. 9, the units4and5may have different widths and/or heights. Indeed, the upper and lower walls41,43of the unit4are shorter in length than the length of the upper and lower walls51,53of unit5, and the outer and inner side walls45,46of unit4are greater in length than the length of the outer and inner walls55,56of unit5.

The height and width differences between the units4and5shown inFIG. 9are not limiting. It may indeed be possible that, for example, that unit5has both a greater height and length than unit4, or that for example unit4has a greater width than unit5but an identical height.

The example shown inFIG. 9may be carried out according to the second manufacturing variant of the rocker2, i.e. by assembling reinforcements on a plate forming the central core3and the flanges6.

However, this example may also be carried out according to the first manufacturing variant of the rocker2, i.e. by assembling two reinforcements so as to form the central core3, the units4and5, and the flanges6.

According to a fourth example, as shown inFIG. 10, the central core3may be inclined at an angle β with respect to the height axis Z. In this example, the angle β may be comprised between 0° and 30°.

The example shown inFIG. 10may be carried out according to the second manufacturing variant of the rocker2, i.e. by assembling reinforcements on a plate forming the central core3and the flanges6.

However, this example may also be carried out according to the first manufacturing variant of the rocker2, i.e. by assembling two reinforcements so as to form the central core3, the units4and5, and the flanges6.

According to a fifth example, as shown inFIG. 11, the flanges may be inclined with respect to the height axis Z

In the example shown inFIG. 11, the flanges6may be parallel. However, the flanges6may also be not parallel. The orientation of the flanges6may be chosen depending on the assembly constraints of the rocker2to the bodywork of the vehicle1.

The example shown inFIG. 11may be carried out according to the second manufacturing variant of the rocker2, i.e. by assembling reinforcements on a plate forming the central core3and the flanges6.

However, this example may also be carried out according to the first manufacturing variant of the rocker2, i.e. by assembling two reinforcements so as to form the central core3, the units4and5, and the flanges6.

According to a sixth example, as shown inFIG. 12, the flanges may be staggered along the width of the rocker2. Indeed, in this example, the central core3comprises two reinforcements. In this example, each of these reinforcements comprises two arms and a bottom, one arm being longer than the other.

The example shown inFIG. 12may be carried out according to the first manufacturing variant of the rocker2, i.e. by assembling two reinforcements so as to form the central core3, the units4and5, and the flanges6.

However, this example may also be carried out according to the second manufacturing variant of the rocker2, i.e. by assembling reinforcements on a reinforced plate forming the central core3and the flanges6, so as to form the units4and5.

The third, fourth, fifth and sixth examples disclosed above may be combined with each other, as well as with the first or second examples disclosed above. Indeed, the first and second examples are examples that are mutually exclusive.

As shown inFIG. 13, the central core3may comprise reinforcements such that it is made more rigid. More specifically, the central core3comprises a lateral rib7situated opposite each of the units4and5along the width axis Y, the lateral rib7may be extending such that it projects opposite the unit4or5. However, inventors have found that an enhanced compromise between mass, rigidity of the central core3and the fact that one unit4or5works in compression whilst the other works in tension, is obtained when the depth of the lateral rib7is a maximum of 20% of the width of the units4or5. Thus, at least 80% of a unit4or5works in compression whilst 80% of the other unit4or5works in tension.

As shown inFIG. 13, each unit may comprise a wall that is transversal with respect to the length of the central core3. The wall may be inclined at an angle α with respect to the height axis Z, the angle α may range between 90° and 105°.

When the value of the angle α is closer to 90°, the material forming any of the units4or5is further away from the neutral deformation axis ψ. In these cases, the material is working (either in compression or tension) if it is further away from the neutral deformation axis ψ, thus resisting the deformation of the rocker2, and absorbing energy. In addition, if the angle α is close to 90°, this creates a segment that will be effective against resisting a force F directed along the width axis Y. Yet, such forces correspond to the main stresses to which the rocker2must resist, as this corresponds to the side impact of the vehicle1by a second vehicle.

FIGS. 14a, 14b, 14care cross-sectional views along the main elongation axis X of a particular example of a rocker2.

As shown in these views, the rocker2may comprise, in this example, a contour frame8, which may be formed, as shown in these figures, by assembling two hat-shaped pieces that may be assembled together. The contour frame8may surround the central core3and the units4and5, and it may be assembled with the central core3at the same level as the flanges6.

As may be seen inFIG. 14a, the rocker2may comprise a first area on which it may only comprise the contour frame8, without the central core3or the units4and5. The first area may be situated on a front portion of the rocker2.

As may be seen inFIG. 14b, the rocker2may comprise a second area on which the rocker2may comprise the contour frame8, the central core3and the units4and5. The central core3may be assembled with the contour frame8through the flanges6. The second area may be situated on a central portion of the rocker2. Alternatively, the second area may extend along the majority of the rocker2.

As may be seen inFIG. 14c, the rocker2may comprise a third area on which the rocker2may comprise the contour frame8, the central core3and only the unit4. The central core3may be assembled with the contour frame8through the flanges6. The third area may be situated on a rear portion of the rocker2.

The rocker2may be made of metal, for example steel or aluminium. Alternatively it may be made of a composite material, for example, with an epoxy resin mould and carbon fibre reinforcements.

According to an example, according to the second manufacturing variant, the central core3may be made of a material with an elastic limit weaker than the material from which the reinforcements R1and R2that form the units4and5may be made.

Furthermore, the central core3may further have a thickness smaller than the thickness of the reinforcements R1and R2.

According to an example, according to the first manufacturing variant, the pieces P1and P2may be manufactured by assembling two elements with different thicknesses that may be joined together, for example by laser welding. According to a possibility of this example, the two elements that form one piece P1or P2may be made of different materials, for example, different grades of steel.

Lastly, for all the examples, the walls that form the units4and5may include a step (level)120,122, such that they become more rigid.

As may be seen inFIG. 15, particularly on the curves ofFIG. 15f, which show the comparison between the performances between two examples of a rocker2according to the present disclosure (shown inFIGS. 15aand 15b) and three rockers according to the state of the art (shown inFIGS. 15c, 15dand 15e), all the rockers having the same mass, a rocker2according to the present disclosure having a maximum bending strength created by the application of a force directed along the width axis Y which is greater, and energy absorption that is likewise better than the rockers of the state of the art.

In order to carry out the simulations, the rocker2shown inFIG. 15amay comprise a UTS-590 steel plate (elastic limit of 390 Mpa) with a thickness of 0.8 mm which forms the central core3, on which two 22MnB5 steel reinforcements R1and R2(elastic limit of 1150 Mpa) with a thickness of 1.5 mm may be assembled.

The rocker2shown inFIG. 15bmay comprise two reinforcements P1and P2which may be assembled to form the central core3and the units4and5. The pieces P1and P2may be formed by a 22MnB5 steel sheet (elastic limit of 1150 MPa) with a thickness of 1.3 mm.

The rocker shown inFIG. 15cmay be formed by a contour frame in which reinforcements R3may be assembled such that they form units. The contour frame may be made from the assembly of a first hat-shaped piece81made of UTS-590 steel (elastic limit of 390 MPa) with a thickness of 0.8 mm, and a second hat-shaped piece82made of 22MnB5 steel with a thickness of 0.8 mm. The reinforcements R3may be Z-shaped reinforcements formed from a 22MnB5 steel sheet with a thickness of 1 mm. Such a rocker may correspond to a known geometry.

The rocker shown inFIG. 15dmay be formed by the assembly of two reinforcements P3and P4so as to form a central core, two units and two flanges. The pieces P3and P4may be made from a 22MnB5 steel sheet with a thickness of 1.4 mm. Such a rocker may correspond to a known geometry.

The rocker shown inFIG. 15emay only be formed by a contour frame made from the assembly of a first hat-shaped piece81made from UTS-590 steel with a thickness of 1.2 mm, and a second hat-shaped piece made from 22MnB5 steel with a thickness of 1.4 mm. Such a rocker may correspond to a classic geometry for rockers that are well known in the state of the art.

The example shown inFIG. 15amay have a maximum bending strength (for bending created by a force −F directed along the width axis Y, and oriented from the inside towards the outside of the vehicle1) which may be 90% higher at the moment of maximum bending (for force −F) than the rocker shown inFIG. 15e. In addition, the example shown inFIG. 15amay have energy absorption higher than 75% compared to the energy absorption of the rocker shown inFIG. 15e, for force −F.

The example shown inFIG. 15amay have a maximum bending strength (for bending created by a force +F directed along the width axis Y, and oriented from the outside towards the inside of the vehicle1) which may be 36% higher at the moment of maximum bending (for force +F) than the rocker shown inFIG. 15e. In addition, the example shown inFIG. 15amay have energy absorption higher than 20% compared to the energy absorption of the rocker shown inFIG. 15e, for force +F.

Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.