Front lower suspension arm

Abstract

The invention relates to a lower suspension arm (16) comprising a stamped metal plate (19) defining a midplane. Said stamped metal plate comprises: a first arm (22) extending to a first connecting end (24); a second arm (28) extending in line with said first arm (22) to a second connecting end (30), said first (22) and second (28) arms extending in an arc, defining an extrados (46, 48) opposite an intrados (38); a third arm (40) projecting from said extrados (46, 48) in line with said second arm (28) opposite said second connecting end (30) and to a third connecting end (42). The said stamped plate (19) exhibits a local thinning (20) in the said first branch (22), near the said second (28) and third (40) branches. Figure to be published with the abbreviation: Fig. 3

Description

Title of the invention: Front lower suspension arm

[0001] The present invention relates to a lower front suspension arm of a motor vehicle.

[0002] The well-known “pseudo MacPherson” type suspensions include a lower triangular suspension arm.

[0003] Typically, the front lower suspension arms comprise a stamped metal plate. This plate includes a first arm extending to a first connecting end adapted to be attached to the front of the motor vehicle on a subframe. This first arm has a circular opening formed in its first end and is hinged on a vertical axis.

[0004] The stamped plate comprises a second arm extending in line with the first arm, opposite the first connecting end and extending to a second connecting end adapted to be attached to a wheel support. The first and second arms extend in an arc, defining an upper surface opposite an inner surface.

[0005] The stamped plate includes a third arm projecting from the upper surface, substantially in a straight line from the second arm opposite the second connecting end, and extending to a third connecting end adapted to be connected to the vehicle cradle forward of the first end. The third connecting end is equipped with a socket allowing it to be articulated on the cradle along a substantially horizontal axis.

[0006] In addition, the arm advantageously includes another stamped plate which is generally joined to the first by welding to mechanically reinforce it.

[0007] The arm must also meet reliability requirements, particularly in terms of endurance and resistance to incidental shocks. The arm must withstand low-intensity shocks, but it must be able to deform without losing its function during high-intensity shocks. During intermediate shocks, the arm must be able to undergo slight plastic deformation.

[0008] However, it is difficult to produce a suspension arm for which the deformation occurs at a predetermined location.

[0009] Also, a problem which arises and which the present invention aims to solve is to provide an arm which can meet the reliability requirements and for which the deformation can be directed in certain areas.

[0010] In order to solve this problem, a lower front suspension arm for a motor vehicle is proposed, comprising a stamped metal plate defining a midplane, said stamped metal plate comprising:

[0011] - a first branch extending to a first end of a suitable connection to be connected to the front of a motor vehicle;

[0012] - a second branch extending in line with said first branch opposite said first connecting end and up to a second connecting end adapted to be connected to a wheel support, said first and second branches extending in an arc defining an extrados opposite an intrados;

[0013] - a third branch extending projecting from said extrados in the continuation substantially straight from said second branch opposite said second connecting end and up to a third connecting end adapted to be connected to said motor vehicle forward relative to said first end.

[0014] And, said stamped plate has a local thinning in said first branch, near said second and third branches.

[0015] Thus, a feature of the invention lies in the use of a stamped metal plate, locally thinned at the first arm to direct the deformation of the lower suspension arm. In this way, during an incidental impact at a high energy level, the arm deforms locally and preferentially in the thinned area of ​​the first arm. This deformation can occur without the arm losing its functionality.

[0016] Furthermore, the arm is subjected to tensile stress during vehicle acceleration, when the first and second arms tend to move apart, and also to compression during deceleration, when the two arms tend to move closer together. The lower arm, and in particular its thinned section, resists deformation during these phases.

[0017] Furthermore, during an incidental shock at an intermediate energy level, the arm can undergo significant plasticization of the material in the thinned area.

[0018] Furthermore, thanks to the implementation of local thinning of the arm, less material is used to manufacture it. Consequently, the mass of the arm is reduced compared to lower suspension arms according to the prior art.

[0019] Preferably, said local thinning extends transversely in said first branch. Thus, the thinning is localized in a highly stressed area of ​​the arm, and more precisely in tension when the vehicle undergoes acceleration, and conversely in compression when the vehicle undergoes deceleration.

[0020] Also, said thinning, and more precisely the corresponding area of ​​the stamped plate, advantageously extends transversely in the first branch in a direction inclined with respect to the line intersecting the second and third connecting ends of the second and third branches respectively. For example, this inclination is between 10° and 30°.

[0021] Furthermore, according to a particularly advantageous feature of the invention, said local thinning has a thickness greater than two-thirds of the thickness of said metal plate. The metal plate has, for example, a thickness between 2.5 mm and 3.5 mm. In other words, the local thinning has a thickness greater than a value between 1.67 mm and 2.33 mm.

[0022] And according to another advantageous feature of the invention, said local thinning has a thickness less than six-sevenths of the thickness of said metal plate. Consequently, if the metal plate has a thickness between 2.5 mm and 3.5 mm, the local thinning has a thickness less than a value between 2.14 mm and 3 mm.

[0023] Advantageously, said metal plate has a thickness greater than two millimeters. For example, its thickness is 3 mm.

[0024] According to a particularly advantageous embodiment of the invention, said first connecting end has a circular opening with a first axis of symmetry substantially perpendicular to said mean plane. The circular opening receives, for example, an elastic connecting element, such as a silent block. In other words, it receives a flexible damping mounting element that filters vibrations.

[0025] Furthermore, said third connecting end is equipped with a mounting sleeve having a second axis of symmetry substantially parallel to said mean plane and oriented towards said first end. The mounting sleeve also advantageously receives an elastic connecting element of the silent block type.

[0026] Advantageously, the stamped metal plate has a single rib extending continuously into the first and second arms. The metal plate has an upper face opposite a lower face. Furthermore, the single rib, which has a substantially square cross-section, projects outward into the lower face. Thanks to this rib, the suspension arm exhibits greater mechanical resistance to deformation.

[0027] Furthermore, the stamped metal plate advantageously has, according to the invention, an internal edge on the intrados of the first and second arms, and this internal edge is oriented relative to the mean plane. Preferably, the internal edge is oriented relative to the underside. In other words, the internal edge is oriented opposite the rib. Such an oriented edge further increases the mechanical resistance to deformation of the suspension arm.

[0028] Furthermore, said stamped metal plate has two external edges extending respectively from said second end to said third end and from said third end to said first end, and said outer edges are oriented with respect to said mean plane. The two outer edges are also oriented with respect to the underside opposite the rib. Advantageously, the two oriented outer edges converge towards each other in the third branch to form a U-shaped section. Also, at the end, the two outer edges are notched to receive a socket which is then welded to them, as will be explained in more detail below.

[0029] Preferably, the arm comprises another stamped plate of substantially the same shape, which is fitted between the raised edges. This other stamped plate is welded inside the aforementioned edges so as to obtain a hollow arm, which is more resistant to mechanical deformation.

[0030] 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:

[0031] [Fig.1] is a partial schematic top view of a motor vehicle equipped with the object of the invention;

[0032] [Fig.2] is a schematic top perspective view of a lower arm of suspension according to the invention; and,

[0033] [Fig.3] is a schematic cross-sectional view of the object in [Fig.2] along plane III - III.

[0034] Fig. 1 shows partially the front left top 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-rear 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 when in a driving situation; and the Z axis extends along a vertical direction, oriented away from the ground.

[0035] Figure 1 schematically represents a chassis element 12 and a body element 14 of the motor vehicle. The chassis element 12 receives a left front lower suspension arm 16, which connects a left front wheel 18 to the chassis element 12.

[0036] A right front lower suspension arm, not shown in [Fig.1], is symmetrical to the left lower suspension arm with respect to a median plane Pm of the motor vehicle, and it also connects a right front wheel and another chassis element, not shown.

[0037] Therefore, we will now refer to [Fig.2] showing, seen from above and in perspective, the lower suspension arm 16 as illustrated in [Fig.1].

[0038] Thus, the lower suspension arm, specific to "pseudo MacPherson" type suspensions, comprises a stamped metal plate 19, which is pre-cut The metal plate 19 is well cut during the stamping process. It has an upper face 15 appearing in [Fig. 2] and a lower face 17, extending behind [Fig. 2].

[0039] Also, prior to the stamping operation, the metal plate 19 has a thinned area 20 whose thickness e is less than the thickness E of the rest of the plate 19. This thinned area 20, which will be detailed below, is obtained, for example, by drawing, or by local rolling, prior to cutting and stamping.

[0040] The stamped metal plate 19 comprises a first arm 22 which extends along a first average direction Dl, to a first connecting end 24, which is enlarged. The first connecting end 24 has a circular opening 26 allowing it to be connected to the frame 12 illustrated in [Fig.1].

[0041] Also, the stamped metal plate 19 includes a second arm 28 which extends in line with the first arm 22 and opposite the first connecting end 24 in a second direction D2 substantially inclined with respect to the first direction D1, at an angle A of less than 170°. The second arm 28 extends to a second spatulated connecting end 30. The latter has three fixing holes 32, 34, 36.

[0042] The first branch 22 and the second branch 28 extend substantially in an arc and they define an intrados 38.

[0043] And the stamped metal plate 19 comprises a third arm 40 of shorter length than the other two arms 22, 28, and which extends substantially in a straight line from the second arm 28 opposite its second connecting end 30. Thus, the third arm 40 extends along a third direction D3 forming an angle B with the second direction D2 of approximately 180°. Furthermore, the third arm 40 extends to a third connecting end 42.

[0044] The first connecting end 24 is spaced from the second connecting end 30 by a distance of approximately 600 mm, for example, while the second connecting end 30 is spaced from the third connecting end 42 by a distance of approximately 360 mm. Also, the first branch 22 and the second branch 28 have widths of approximately 70 mm, for example.

[0045] In addition, a continuous rib 44 with a substantially square cross-section is formed in the first 22 and second 28 branches. The rib 44 then projects from the lower face 17. This rib 44 is intended to increase the mechanical resistance to deformation of the arm. It has a bend to follow the curvature of the two branches 22, 28 relative to each other.

[0046] Also, opposite the intrados 38, the stamped metal plate 19 has two extrados portions, a first portion 46 extending between the first branch 22 and the second branch 40, and a second portion 48 extending between the second branch 28 and the third branch 40.

[0047] And the stamped metal plate 19 has an internal border 50 in the intrados 38, which internal border is erect with respect to the average plane defined by the stamped plate 19, and more precisely with respect to its lower face 17. In other words, the internal border 50 extends opposite the continuous rib 44.

[0048] On the contrary, the stamped metal plate 19 has a first portion of external edge 52 corresponding to the first portion 46 of extrados and a second portion of external edge 54 corresponding to the second portion of external edge 48. The two portions of external edge 52, 54 are erect with respect to the inner face 17 partially opposite the rib 44.

[0049] The two outer rim portions 52, 54 also converge towards each other in the third branch 40 to form a U-shaped end. The ends of these two outer rims 52, 54 are notched to receive a sleeve 56. The latter is welded to it.

[0050] A feature of the invention lies in the implementation of the thinned zone 20, which extends transversely in the first branch 22 towards the second and third branches 28, 40. The thinned zone 20 is here delimited by two parallel dashed lines, L1 and L2.

[0051] It will be observed that the thinned area 20 extends in a direction forming an angle close to 20° with the line cutting the second 30 and the third 42 ends respectively of the second 28 and third 40 branches.

[0052] Reference will be made to [Fig.3] showing the suspension arm 16 and its cross-section along the section line III - III illustrated in [Fig.2], to describe more precisely the thinned area 20.

[0053] We find on this [Fig.3], the first branch 22 and the third branch 40.

[0054] Also partially visible are the inner edge 50 and the second portion of the outer edge 54. And the thinned area 20 of the stamped plate 19 is found between two perpendicular lines PI, P2 intersecting respectively the intersection of the cutting line III - III and the two parallel lines L1, L2. And in this area, the thickness e is less than the thickness E of the rest of the plate 19.

[0055] However, it will be observed that the thickness of the stamped plate 19, along the outer edges of the two parallel lines L1, L2 appearing on [Fig.3], varies progressively away from the smallest thickness e to the largest thickness E. These edges correspond to two transitional zones, 58, 60 bordering the thinned zone 20.

[0056] In the example shown in [Fig.3], the thinned area 70 has a thickness e of 2.2 mm. And the areas of greater thickness E have a thickness of 3 mm.

[0057] We will refer again to [Fig.2] in order to specify the constraints which are exerted on the suspension arm 16.

[0058] First of all, it will be observed that the sleeve 56 allows to receive a silent block and to connect the third connecting end 42 of the third branch 40, to the chassis element 12 according to a pivot connection whose axis is substantially parallel to the longitudinal axis X.

[0059] The circular light 26 of the first end 24 of the first branch 22 is also adapted to receive a silent block to connect the first connecting end 24 to the chassis element 12 behind the third connecting end 42. The axis of this last silent block extends in a substantially vertical direction.

[0060] And, the three mounting holes 32, 34, 36 of the second connecting end 30 allow it to be connected to a wheel support or a spindle. This second connecting end 30 is commonly called: ball joint center.

[0061] Thus, in the event of a collision, generally when the wheel of the vehicle 18 encounters an obstacle, the second arm 28 tends to be pulled towards the first arm 22. And to cushion this collision, the suspension arm 16 tends to deform preferentially in the thinned area 20. In this way, the anchoring elements of the chassis elements 12 are preserved to a certain extent.

[0062] Furthermore, the thinned area 20 promotes the lightening of the suspension arm 16, and therefore, the weight of the vehicle.

[0063] Depending on the choice of the desired fusibility zone for shock resistance, other locations for the thinned zone can be chosen and implemented, for example closer to the zone connected to the wheel, near the second spatulated end of the connection 30.

Claims

Demands

1. Lower front suspension arm (16) of a motor vehicle comprising a stamped metal plate (19) defining a mean plane, said stamped metal plate comprising: - a first arm (22) extending to a first connecting end (24) adapted to be connected to the front of a motor vehicle; - a second arm (28) extending in the continuation of said first arm (22) opposite said first connecting end (24) and to a second connecting end (30) adapted to be connected to a wheel support, said first (22) and second (28) arms extending in an arc defining an extrados (46, 48) opposite an intrados (38);- a third branch (40) extending outward from said extrados (46, 48) in a substantially straight line from said second branch (28) opposite said second connecting end (30) and up to a third connecting end (42) adapted to be connected to said motor vehicle forward relative to said first end (24); characterized in that said stamped plate (19) has a local thinning (20) in said first branch (22), near said second (28) and third (40) branches.;

2. Front lower suspension arm according to claim 1, characterized in that said local thinning (20) extends transversely in said first arm (22).

3. Lower front suspension arm according to claim 1 or 2, characterized in that said local thinning (20) has a thickness e greater than two-thirds of the thickness E of said metal plate (19).

4. Front lower suspension arm according to any one of claims 1 to 3, characterized in that said local thinning (20) has a thickness e less than six-sevenths of the thickness E of said metal plate (19).

5. Front lower suspension arm according to any one of claims 1 to 4, characterized in that said metal plate (19) has a thickness E greater than two millimeters.

6. Front lower suspension arm according to any one of claims 1 to 5, characterized in that said first connecting end (24) has a circular opening (26) of a first axis of symmetry substantially perpendicular to said mean plane.

7. Front lower suspension arm according to any one of claims 1 to 6, characterized in that said third connecting end (42) is equipped with a fixing sleeve (56) having a second axis of symmetry substantially parallel to said mean plane and oriented towards said first end (24).

8. Front lower suspension arm according to any one of claims 1 to 7, characterized in that said stamped metal plate (19) has a single rib (44) extending continuously into said first (22) and second (28) arms.

9. Front lower suspension arm according to any one of claims 1 to 8, characterized in that said stamped metal plate (19) has an internal border (50) in the intrados (38) of said first (22) and second (28) arms, and in that said internal border is erect with respect to said mean plane.

10. Front lower suspension arm according to any one of claims 1 to 9, characterized in that said stamped metal plate (19) has two external edges (52, 54) extending respectively from said second end (30) to said third end (42) and from said third end (42) to said first end (24), and in that said external edges (52, 54) are erect with respect to said mean plane.

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