COMPOUND ARM AXLE STRUCTURE

Description

[0001] The present invention relates to a torsional axle structure for a motor vehicle.

[0002] Common rear axles on motor vehicles include a pair of suspension arms that connect the rear wheel carriers to the vehicle body. The two suspension arms are pivotally mounted to the body and extend towards the rear of the vehicle. These two opposing suspension arms are connected to each other by a crossmember.

[0003] This type of axle is commonly used at the rear of passenger vehicles. The axle beams are subjected to both high stresses during driving and large-amplitude deformations to control oscillations on side slopes, as well as the camber and steering movements induced by this slope. The beams are usually open-profile, and in particular U-shaped. They have a bottom and two free flanges facing each other. They also have two opposing ends, each with a bottom edge and two flange edges. Notches are cut into the flange edges to form a pair of notches.

[0004] Thus, each end of the crossbar receives an arm which then extends into the pair of notches where it is welded.

[0005] In addition, at each end of the cross member, a longitudinal connecting piece, or gusset, is installed inside the cross member so that the two opposite longitudinal edges of the connecting piece are respectively connected to the wings of the cross member, while one of the two ends of the connecting piece is connected to the corresponding arm.

[0006] The cross members and longitudinal connecting pieces are made from stamped and welded blanks. These blanks are cut from strips of metal material of a constant thickness. The thicknesses are then chosen to meet the fatigue and wheel impact resistance criteria in the most stressed areas of the axle. Consequently, in the less stressed areas, and particularly in the areas further from the junction between the cross member and the arms, the fatigue resistance is well above the required thresholds. Therefore, the excess material is unnecessary and costly.

[0007] Document JP 2016 101849 A discloses a torsible axle structure of a motor vehicle according to the preamble of claim 1. Documents JP 2012 111440 A, KR 102 267 135 B1, KR 101 338 966 81 disclose other torsible axle structures of motor vehicles.

[0008] Also, a problem that arises and that the present invention aims to solve is to provide a more economical torsional axle.

[0009] In order to solve this problem, a torsional axle structure for a motor vehicle is proposed comprising: a U-shaped cross member having, on the one hand, a bottom and two free flanges and on the other hand, two opposite cross member ends and a middle portion, each of said two ends having a bottom edge and two flange edges, said flange edges each having an arc-shaped notch to form a pair of notches; a hollow arm connected to each of said two opposite ends and extending into said pair of notches; and, a longitudinal connecting piece having two opposite piece ends and two opposite longitudinal edges, and mounted to each of said two cross member ends so that said two opposite longitudinal edges are respectively connected to said flanges inside said cross member, while one of said two piece ends is connected to said corresponding arm.

[0010] The connecting piece then has a decreasing thickness from one of the two ends of the piece connected to the arm to the other end. Thus, a feature of the invention lies in the implementation of a longitudinal connecting piece, called a gusset, having a decreasing thickness from its end connected to the arm to its opposite end, which extends into the crossmember. In this way, the connecting piece has the required thickness in the area where it joins the arm to meet the fatigue or wheel impact resistance criteria where they are more demanding, while it is thinner towards its opposite end where it is subjected to less stress.

[0011] As a result, the connecting part contains less material and is therefore less expensive. Furthermore, the axle is lighter, which also reduces the vehicle's weight and thus its fuel consumption.

[0012] Thus, the fatigue resistance of the different parts of the axle is locally adapted to the required fatigue resistance thresholds.

[0013] Furthermore, said cross member is preferably obtained by stamping a metal strip having a decreasing thickness from two strip ends corresponding to said two cross member ends towards a median area corresponding to said median part.

[0014] Thus, in addition to the gusset plate, the crossmember itself features a progressively thicker metal sheet from its midsection to its two ends. This design makes the crossmember more resistant to fatigue in the areas where it connects to the suspension arms, where it is subjected to greater stress, and less resistant in its midsection, where it is subjected to less stress. Consequently, the amount of material required to manufacture the crossmember is reduced, thus lowering its cost. Furthermore, the weight of the vehicle on which it is installed is also reduced.

[0015] According to a particularly advantageous embodiment of the invention, said connecting piece has a first portion including said other end of piece and a second portion including said one of said two ends of piece, and said first portion has a first thickness e1,while said second portion has a second thickness e2 greater than said first thickness e1. According to this method of implementation, the connecting piece has two portions of substantially equal lengths, with a greater thickness in the portion including the end of the piece connected to the arm.

[0016] Preferably, said connecting piece has an intermediate portion between said first portion and said second portion, and said intermediate portion has an intermediate thickness ei included between e1 And e2.Thus, the connecting piece has three successive sections of different thicknesses. Such a piece can, for example, be obtained by starting with a blank that is rolled differently depending on the length of the piece. In other words, the blank is rolled less to obtain a certain thickness in the section including one of the two ends of the piece that is connected to the arm. It is rolled less in the section including the opposite end. And it is rolled to an intermediate thickness in the middle section.

[0017] It can also be achieved by joining several metal plates together. For example, a first blank of thin thickness, extending to a length equivalent to the maximum length of the connecting piece, is provided. A second blank of the same thin thickness, of intermediate length, is provided and welded to the first blank up to one end. A third blank of the same thin thickness, even shorter, is then welded to the second at the end of the first.

[0018] According to another embodiment, three blanks of different thicknesses are joined end-to-end successively. A first blank of thin thickness is provided, its length corresponding to the thin section of the connecting piece. A second blank of greater thickness is provided, its length corresponding to the length of the middle section of the connecting piece. The second blank is then welded to the end of the first blank, extending from it. A third blank of even greater thickness is provided, its length corresponding to the length of the last section of the connecting piece. The third blank is then welded to the end of the second blank, opposite the first blank.

[0019] According to a particularly advantageous embodiment of the invention, the bottom edge and one of the two ends of the part extend in opposite directions with respect to the arm. In this way, the arm engages between the end of the connecting part and the bottom of the U-shaped profile at the bottom edge. It rests in the pair of arc-shaped notches. Furthermore, the arm and the cross member are welded together at the junction of the notches, and the connecting part is welded at its end to the arm, while on the opposite side, the bottom edge and the arm are joined together by at least one weld bead.

[0020] Also, the other end of the part is connected to the base. In other words, the other end of the part, opposite the one connected to the arm, is welded to the base. Thus, the connecting part is mounted at an angle inside the cross member. It closes the U-shaped profile at its end. Consequently, the rigidity of the cross member end is increased.

[0021] Furthermore, preferably, the connecting piece has two opposing edges curved towards each other, forming the two opposing longitudinal edges. Advantageously, the two edges are curved parallel to each other so that they can lie flat against the two flanges of the cross member. Thus, two weld beads are provided at the joints of the edges and the flanges in contact to ensure perfect rigidity of the assembly.

[0022] Preferably, the connecting piece has a fold along a line perpendicular to the opposite longitudinal edges and at a distance from one of the two ends of the piece. Thus, the connecting piece has a portion including one of the two ends of the piece, which is connected to the arm, and which is substantially folded relative to the rest of the connecting piece. In other words, this portion is folded, for example, at an angle of less than 20° to the rest of the piece along a line intersecting the piece and extending perpendicularly from the longitudinal edges. Thus, and as will be explained in more detail later in the description, the folded portion extends substantially parallel to the base and away from it. In this way, the end of the U-shaped cross member and the folded portion form substantially a square-based cylinder. This further stiffens the end of the cross member.

[0023] Also, these two curved edges extend outside the fold. Thus, it is understood that the curved edges extend outside the volume formed by the connecting piece and the cross member, while the folded portion is substantially parallel to the bottom of the cross member. In this way, it is easier to weld the edges of the connecting piece to the two flanges opposite the cross member.

[0024] According to another particularly advantageous feature of the invention, one of the two ends of the part extends in a T-shape perpendicular to the wings. In this way, the interface with the arm has a larger surface area, thus allowing for a longer weld bead around the end. This results in a firmer connection of the end to the arm.

[0025] 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 attached drawings in which: [ Fig. 1 ] is a partial schematic top view of a torsible axle according to the invention; [ Fig. 2 ] is a partial schematic view from below of a torsional axle according to the invention; [ Fig. 3 ] is a schematic front view of an element of the object of the [ Fig. 2 ] ; ] Fig. 4 ] is a schematic perspective view along arrow IV of the object of the [ Fig. 3 ] ; ] Fig. 5 ] is a schematic side perspective view of another element of the object of the [ Fig. 2 ] ; ] Fig. 6 ] is a schematic perspective view along arrow VI of the object of the [ Fig. 5 ] ; And, [ Fig. 7 ] is a schematic cross-sectional view of the object of the [ Fig. 6 ] according to plan VII-VII.

[0026] There [ Fig. 1 [The figure] partially shows a torsional axle structure 10 having a cross member 12. The cross member 12 has a left end 15 connected in a T-junction to a left suspension arm 14. The suspension arm 14 has a front end equipped with a bushing 16 for rotational mounting on a motor vehicle chassis. At the opposite end, the suspension arm 14 has a rear end fitted with a wheel support 18. A left spring cup 20 is mounted integrally with the cross member 12 and the arm 14, in the angle formed by the left end 15 of the cross member 12 and the rear end of the suspension arm 14.

[0027] Cross member 12 has on the opposite side, a right end 22, symmetrical to the left end 15 with respect to a median part 24. Thus, the right end 22 of the cross member 12 is symmetrically equipped with a right arm and a right spring cup.

[0028] We find on the [ Fig. 2 ], the torsional axle structure 10 as illustrated on the [ Fig. 1 ], view from below. We can see the crossmember 12, the left suspension arm 14 and the left spring cup 20.

[0029] Also, the cross member 12 has a U-shaped profile section. It includes a base 26 and two wings 28, 30 erected opposite each other with respect to the base 26.

[0030] In addition, a connecting piece 32, also called a gusset, is engaged inside the cross member 12 in the left end 15 and it extends to the left arm 14.

[0031] Obviously, the same connecting piece, not shown, is engaged inside the crossbar at its right end in a symmetrical manner to extend to the right arm.

[0032] We will refer to the [ Fig. 3] et [Fig. 4 ] to describe in detail the left end 15 of traverse 12.

[0033] We find on the [ Fig. 3 ] the left end 15. One of the wings 30, ending with a first wing edge 34, and the bottom 26 appear. Thus, the bottom 26 has a bottom edge 36. A first arc-shaped notch 38 is formed in the wing edge 34. The first arc-shaped notch 38 has a predetermined radius of curvature corresponding approximately to the radius of curvature of the semi-periphery of the arm 14 as will be explained below.

[0034] We find on the [ Fig. 4 ] the left end 15 of the cross member 12, and in particular the two opposite wings 30, 28 as well as the bottom 26.

[0035] Furthermore, we also find the bottom edge 36 and the first arc-shaped notch 38 formed in the first wing edge 34. Also, on this [ Fig. 4 ] appears a second wing edge 40 of the other wing 28 in which is made a second arc notch 42, symmetrical to the first arc notch 38 with respect to a mean plane Pm cutting longitudinally the bottom 26 and extending between the two wings 28, 30.

[0036] Furthermore, the right end 22 of the cross member 12 shown on the [ Fig. 3 ] is symmetrical from the left end 15 with respect to the median plane PM intersecting the cross member 12 in the median part 24.

[0037] Furthermore, the cross member is obtained by stamping a metal blank, for example, made of steel. The thickness of this metal blank increases from the central section 24 towards the two opposite ends 15 and 22. The metal blank intended for stamping the cross member 12 is, for example, divided into six equal lengths. Thus, the first two proximal sixths, corresponding to the central section 24 of the cross member 12, have a thickness of 3 mm, for example. The next two sixths of the metal blank, symmetrical to each other with respect to the first two proximal sixths, have a thickness of 4 mm. And the last two distal sixths, corresponding respectively to the two opposite ends 15 and 22, have a thickness of 5 mm. These thickness values ​​are given for guidance only and are not exhaustive.

[0038] Such localized thinning of the blanks can be achieved by stretching or by crushing, for example by rolling.

[0039] We will now refer to the [ Fig. 5], [Fig. 6 ] And [ Fig. 7 ] to describe in detail the connecting piece 32.

[0040] Thus we find on the [ Fig. 5 [ ], the connecting piece 32 seen from the side. It extends longitudinally from a first end 44 to a second end 46. It has two opposing longitudinal edges 48, 50 facing each other. The two upright longitudinal edges 48, 50 define two opposing edges separated from each other by a distance corresponding to the distance that separates the two wings 28, 30 from the cross member 12 at the two opposing ends 15, 22.

[0041] Also, the connecting piece 32 has a fold along a transverse line T substantially perpendicular to the two longitudinal edges 48, 50, and located substantially at two-thirds 56, 58, of the piece from the first end 44. Thus, a last third 60 of the piece including the second end 46 is inclined with respect to the first two-thirds 56, 58 extending in the same plane, at an angle 52 substantially less than 20°, for example 15°.

[0042] Furthermore, the second end 46 of the connecting piece 32 extends in a T-shape substantially perpendicular to the longitudinal edges 48, 50. In other words, the second end 46 has a width greater than the width which extends between the two edges 48, 50 of the connecting piece 32.

[0043] We find on the [ Fig. 6 ], the connecting piece 32 seen from its first end 44 and we find its second end 46 which extends transversely on each side of the two borders 48, 50.

[0044] Also, it will be observed that the connecting piece 32 has a central embossed area 54 which allows it to be made more rigid.

[0045] We will now refer to the [ Fig. 7 showing in longitudinal section along the section plane VII-VII shown on the [ Fig. 6 ], connecting piece 32.

[0046] The connecting piece 32 is made by stamping a metal blank of varying thicknesses. Thus, in the example shown on the [ Fig. 7 ], the resulting connecting piece 32 has three different thicknesses in the three portions of the piece corresponding respectively to the three thirds 56, 58 and 60 of the connecting piece 32. Thus, the first portion of the piece corresponding to the first third 56 has a thicknesse1, for example, 3 mm. The third portion of the piece, corresponding to the last third (60), has a thickness e2, for example, 5 mm. And, the second portion of the piece, corresponding to the second third 58, has an intermediate thickness ei, for example, 4 mm.

[0047] In other words, the thickness of the connecting piece 32 increases, here in three steps, from its first end 44 to its second end 46. A progression in two steps or in more than three steps can be implemented.

[0048] In addition, continuous progression can also be implemented.

[0049] Also, the thickness values ​​are given for guidance purposes only and are not exhaustive.

[0050] We will refer again to the [ Fig. 2 ] in order to describe more precisely, the implementation of the connecting piece 32 at the left end 15 of the cross member 12.

[0051] Thus, the second T-shaped end 46 of the connecting piece 32 extends in support on the left suspension arm, while its first end 44 extends in support against the bottom 26 of the cross member 12.

[0052] Also, the third portion of the piece corresponding to the last third 60 of the connecting piece 32 extends substantially parallel to the bottom 26 of the cross member 12 along the free edges of the two opposite wings 28, 30, while the first two portions corresponding to the first and second portions are inclined to converge towards the bottom 26.

[0053] Also, conversely, as illustrated on the [ Fig. 1 ], the bottom 26 comes, at the level of the bottom edge 36, to be applied to the suspension arm 14 opposite the second end 46 of the connecting piece 32.

[0054] Furthermore, we will observe on the [ Fig. 2] that the two upright longitudinal edges 48, 50 of the connecting piece 32 come respectively in support against the two wings 28, 30.

[0055] Thus, in this relative position of the cross member 12, the suspension arm 14 and the connecting piece 32, the assembly is welded, in particular, at the joints between the two upright longitudinal edges 48, 50 and the two wings 28, 30, between the first end 44 and the bottom 26, between the second end 46 and the suspension arm 14, and on the opposite side, along the bottom edge 36, between the bottom 26 and the suspension arm 14. In addition, the left spring cup 20 is also welded to the suspension arm 14 and to the left end 15 of the cross member.

[0056] Thus, the whole is perfectly rigid and the connecting piece 32 reinforces the left end 15 of the cross member 12 to which the suspension arm 14 is attached.

[0057] Thus, the connecting piece 32 is thicker in its third portion, corresponding to the last third 60, in the connection area between the left end 15 of the cross member 12 and the left suspension arm 14, where it is subjected to the greatest mechanical stress. Conversely, at the other end 44 of the connecting piece 32, where it is subjected to less stress, the thickness is less.

[0058] In this way, the material costs of the connecting part 32 are significantly reduced, and in addition, the weight of the axle is reduced.

[0059] The cross member 12 described above aims to achieve the same objective. However, a cross member with a constant stamped sheet thickness can also be implemented with a connecting piece 32 as described above.

Claims

1. Motor vehicle torsion axle structure (10), comprising: - a U-shaped cross-member (12) having, on the one hand, a bottom (26) and two free flanges (28, 30) and, on the other hand, two opposite cross-member ends (15, 22) and a middle part (24), each of said two ends having a bottom edge (36) and two flange edges (34, 40), said flange edges each having an arc-shaped notch (38, 42) so as to form a pair of notches; - a hollow arm (14) connected to each of said two opposite ends (15, 22) and extending in said pair of notches (38, 42); - a longitudinal connecting piece (32) having two opposite piece ends (44, 46) and two opposite longitudinal edges (48, 50), and being mounted at each of said two cross-member ends (15, 22) in such a way that said two opposite longitudinal edges (48, 50) are respectively connected to said flanges (28, 30) inside said cross-member (12), while one (46) of said two piece ends is connected to said corresponding arm (14); characterized in that said connecting piece (32) has a thickness that decreases from said one (46) of said two piece ends that is connected to said arm (14) to the other piece end (44).

2. Torsion axle structure according to Claim 1, characterized in that said cross-member (12) is obtained by stamping a metal strip having a thickness that decreases from two strip ends corresponding to said two cross-member ends (22, 15) towards a middle zone corresponding to said middle part.

3. Torsion axle structure according to Claim 1 or 2, characterized in that said connecting piece (32) has a first portion including said other piece end (22) and a second portion including said one of said two piece ends (15), and in that said first portion has a first thickness e1, while said second portion has a second thickness e2 that is greater than said first thickness e1.

4. Torsion axle structure according to Claim 3, characterized in that said connecting piece (32) has an intermediate portion between said first portion and said second portion, and in that said intermediate portion has an intermediate thickness ei that is between e1 and e2.

5. Torsion axle structure according to any one of Claims 1 to 4, characterized in that said bottom edge (36) and said one of said two piece ends (46) extend opposite one another with respect to said arm (14).

6. Torsion axle structure according to any one of Claims 1 to 5, characterized in that said other piece end (44) is connected to said bottom (26).

7. Torsion axle structure according to any one of Claims 1 to 6, characterized in that said connecting piece (32) has two opposite edges (48, 50) curved towards one another and forming said two opposite longitudinal edges.

8. Torsion axle structure according to any one of Claims 1 to 7, characterized in that said connecting piece has a bend along a line T perpendicular to said opposite longitudinal edges (48, 50) and at a distance from said one (46) of said two piece ends.

9. Torsion axle structure according to Claims 7 and 8, characterized in that said two curved edges (48, 50) extend on the outside of said bend.

10. Torsion axle structure according to either one of Claims 7 and 9, characterized in that said said one (46) of said two piece ends extends in a T-shape perpendicularly to said edges (48, 50).