FR2858585A1 - Motor vehicle e.g. sedan, axle, has anti-banking bar whose one end is integrated with associated longitudinal arm due to torsion of arms end around axis parallel to associated arm - Google Patents

Abstract

The axle (1) has two longitudinal arms (2, 3) that are transversely linked by a crossbeam and an anti-banking bar (5). Two ends of the bar are integrated with respective sides of the arms, such that the bar provides a torsional rigidity about an axis parallel to an axis of the bar. One end of the bar is integrated with associated arm due to the torsion of the arms end around an axis parallel to the associated arm.

Description

SOFT AXLE FOR MOTOR VEHICLE

  The present invention relates to a so-called flexible axle for a motor vehicle.

  Such an axle comprises two longitudinal arms, connected transversely by at least one cross member and an anti-roll bar, a first end of the anti-roll bar being secured to one face of a first longitudinal arm, the second end of the anti-roll bar being secured to one side of the second longitudinal arm, so that the anti-roll bar gives the flexible axle torsional rigidity about an axis substantially parallel to the axis of this bar.

  This type of flexible axle, corresponding to an "H" profile, offers handling performance of a very satisfactory level for the volume it occupies, which is lower than that of a multi-link type train. . This small footprint, which makes it easily compatible with any rear axle architecture, and the low cost of its implementation, mainly by welded-type assemblies, have led to an important deployment of the flexible axle technique by the engineers. Car manufacturers.

  Flexible axles are thus used on all types of vehicles and more and more on heavy vehicles, for which multi-link trains were previously preferred. In this type of vehicle (large sedan, minivan or commercial vehicle), some elements of the anti-roll bar are close to their absolute limits of operation, due to the large mass of the vehicle and the desire for optimal performance. However, the anti-roll bar is one of the most difficult components to develop, especially in terms of endurance. In addition to holding the body of the bar, the connection areas of the ends of the anti-roll bar on the arms, generally welded, are particularly stressed and require the attention of designers under penalty of premature rupture of the link.

  Some solutions have been applied to flexible axles in the past to improve the endurance performance of this link. These solutions revolve around the fact that during a loading on a slope, in addition to the expected stress in torsion, the anti-roll bar is also subjected to a large bending tending to deform it into "S" in a vertical plane. This stress has no functional value and has a predominant influence on the behavior of the weld beads between the anti-roll bar and the longitudinal arms. FR-A-2795681 discloses and shows an oblong section anti-roll bar to reduce the amount of cant bending in the overall load. However, this technique is limited by manufacturing constraints, the flattening of the anti-roll bar can not exceed a critical value beyond which cracks start inside the bar and significantly degrade its performance. endurance.

  One of the objectives of the invention is therefore to propose a flexible axle 20 making it possible to reduce the amount of deflection of the anti-roll bar with respect to a transverse axis of the vehicle, without reducing its main torsional performance around a same transverse axis. According to the objectives of each manufacturer, the flexible axle must also be compact, inexpensive and easy to integrate into the vehicle environment.

  To meet these objectives, the invention proposes a flexible axle of the type described above, characterized in that an end of the anti-roll bar is secured to the associated longitudinal arm by means of an elastically deformable blade so as to allow a twist of said end of the anti-roll bar about an axis substantially parallel to the associated longitudinal arm.

  This elastically deformable blade can then be a portion of said face of the longitudinal arm, delimited by zones of weakness, so as to obtain these physical characteristics without adding parts, and therefore 1o weight, intermediate. In addition, the fact that the deformable blade is a portion of the arm face allows an implantation of this blade on any type of longitudinal arm, regardless of the general architecture of the associated suspension of the vehicle.

  According to a first embodiment of the invention, the hollow arm 15 has at least two walls substantially parallel to the median plane of the vehicle, and the weakening zones are made by thinning the thickness of the wall corresponding to said arm face. These thinning can be performed on the inner surface of said wall.

  According to a second embodiment of the invention, the weakening zones 20 consist of through holes.

  According to one characteristic of the invention, the weakening zones formed in the face of the longitudinal arm on which the anti-roll bar is secured extend to other faces of the same longitudinal arm.

  According to one characteristic of the invention, the end of the anti-roll bar is made integral with the inner lateral face of the longitudinal arm, oriented towards the other longitudinal arm, and the weakening zones are formed in this inner side face.

  The cross-member may be a "U" -shaped profile inside which the anti-roll bar is housed, and the weakening zones are then formed in the face of the longitudinal arm, also inside the zone delimited by the profile of this cross.

  According to one characteristic of the invention, the end of the anti-roll bar is made integral with the outer lateral face of the longitudinal arm, facing away from the other longitudinal arm, and the weakening zones are formed in this embodiment. outer side face, and in the inner side face of the same longitudinal arm.

  According to one characteristic of the invention, the flexible axle has a general design symmetry with respect to a longitudinal and vertical median plane, with a resiliently deformable blade integral with each longitudinal arm.

  Other features and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: FIG. 1 is a schematic representation of a flexible axle according to FIG. FIG. 2 is a schematic representation of the principle of the invention, FIG. 3 is a perspective view of a flexible axle according to the invention according to a first embodiment, FIG. 3a is a section of FIG. of the flexible axle shown in Figure 3, in a vertical plane and in the axis of the anti-roll bar.

  FIG. 4 is a view similar to that of FIG. 3 according to a second embodiment, FIG. 4a is a section of the flexible axle shown in FIG. 4, in a vertical plane and in the axis of the anti-roll bar.

  FIG. 4b is a section similar to that of FIG. 4a, according to a variant embodiment of the invention; FIG. 5 is a section of the flexible axle according to a first variant of the second embodiment, according to a vertical plane and in the axis of the anti-roll bar - Figure 6 is a view similar to that of Figure 3 according to a second variant of the second embodiment, - Figure 7 is a view similar to that of Figure 3 according to a third variant of the second embodiment, - Figures 8a, 8b, 8c and 8d are schematic representations of different design variants of the weakening zones according to the invention.

  In the following description, a longitudinal, vertical and transverse orientation according to the orientation conventionally used in the automobile and indicated by the trihedron L, V, T of the various figures will be adopted without limitation.

  As shown in Figure 1, a rear flexible axle 1 consists of two longitudinal arms 2 and 3, connected by a front cross member 4.

  Advantageously, the longitudinal arms have the shape of hollow tubes with at least two so-called lateral walls 21 and 22, substantially parallel to the median vertical plane of the vehicle. It will be understood, however, that the present invention can be applied to other forms of arms. Parallel to the crossbar 4, a rear anti-roll bar 5 extends from one longitudinal arm 2 to the other 3. Such a flexible axle 1 having a symmetry along the vertical median plane of the vehicle, that is to say the plane comprising the median longitudinal axis xx 'and a vertical axis, only the right half of this flexible axle will be described later and shown in Figures 2 to 8. It will be understood that by symmetry, this description and this representation s also apply to the left half of the flexible axle according to the invention.

  A front end of the longitudinal arm 2 is hinged under the body of the vehicle via a bearing 6 and the rear end of the longitudinal arm 2 is connected to a wheel support 7. substantially equidistant from the wheel support 7 and the bearing 6, a lateral end 51 of the anti-roll bar 5 is welded to one of the side walls 21 of the longitudinal arm 2. It will be understood that according to the architecture of the suspension of the vehicle and the desired performance for the anti-roll bar 5, it may be envisaged, as shown in Figure 5, to have a length of bar such that it must be welded to the outer side wall 22 of the arm 2, that is to say the wall which is oriented opposite the other longitudinal arm 3.

  According to the invention, in order to obtain an elastically deformable blade 10 for fixing the anti-roll bar 5, weakenings 11 of the wall 21 of the arm 2, on which the anti-roll bar 5 has been welded, are produced. by reducing the thickness of the wall 21 in a substantially longitudinal direction, so as to give this zone a degree of torsional flexibility about a substantially longitudinal axis. A schematic diagram of the behavior of this blade 10, when the vehicle is loaded in cant, is thus represented in FIG.

  According to a first embodiment, of the type shown in FIG. 3, the attenuations 11 are through holes 12 located in the lateral wall 21 on which the anti-roll bar 5 is welded. A second embodiment of these attenuations 11 of the type shown in FIG. 4 can be obtained by reductions 13 in the thickness of this side wall 21. By way of example, FIG. 4a shows such thickness reductions 13 made in the inner side wall 21. , on the outer face 21e of this 1o wall 21. Such an embodiment by reductions 13 of thickness makes it possible not to create openings 12 in the arms 2 and not having to take care of filling the through holes 12 for sealing or corrosion issues. Thus, it will be noted that the embodiment in which the losses 11 are obtained by through holes 12 should preferably be accompanied, after welding of the end 51 of the anti-roll bar 5 to the arm 2, a closure of the openings 12 for example by a deformable material, and / or plastic plugs, not shown. It will be understood that during the manufacture of the longitudinal arm 2, the thickness reductions 13 may be made in the inner face 21i of this wall 21. This variant embodiment, shown in FIG. 4b, also has the advantage to allow weld beads around the bar 5 anti-roll thicker. An alternative embodiment, not shown, to obtain these thicker weld seams is to achieve the thickness reductions 13 in the outer face 21e of the wall 21, and weld the bar 5 on the inner face 21i. In this case, the longitudinal arm 2 will be made of two welded parts to allow this welding of the bar 5 inside the arm 2.

  In the case of an anti-roll bar 5 welded to the outer lateral wall 22 of the arm 2, and therefore of a roll-bar 5 traversing transversely the longitudinal arm 2, weakenings 11 are produced jointly in the outer lateral wall. 22. However, the inner side wall 21 must be able to accompany the torsion movement of the anti-roll bar 5 about a substantially longitudinal axis, movement permitted by the elastically deformable blade 10 formed in the outer side wall 22. As shown in FIG. shown in Figure 5, the inner side wall 21 must therefore have an opening whose diameter is sufficient to 0o allow the clearance of the anti-roll bar 5, that is to say at least greater than the diameter of the bar 5.

  Each of the ends 51 of the anti-roll bar 5 is connected to a longitudinal arm 2, as well as the crossbar 4. According to the agcnccmcnts made on the rear axle of the vehicle, and in the form of the crossbar 4, the bar anti15 cant 5 can then be housed inside the crossbar 4 (Figure 6 shows such a train architecture, with a cross section U>).

  In this case, the elastically deformable blade 10 must be made only in the inner side walls 21 if the anti-roll bar 5 is welded to the inner side wall 21, or outer 22 if the anti-roll bar 5 is welded to the outer side wall 22. In the case where the part of the arm 2 on which the end 51 of the bar 5 is welded is not located in the region of the front cross member 4, the elastically deformable blade 10 can be obtained by weakened 11 made in several consecutive faces. In this case, shown in FIG. 7, the main direction of the weakens 11 must remain in a substantially longitudinal direction, in order to allow the torsion bar 5 to be twisted about an axis along this direction.

  The working zone comprised between the weakenings 11 combines a good torsional flexibility about the longitudinal axis of the vehicle, and a high torsional stiffness around the transverse direction. It therefore directly responds to the various objectives of the invention set forth above, since it considerably limits the adverse effects of bending without affecting the torsion of the anti-roll bar 5 which is substantially fully transmitted. The different embodiments of the invention make it possible, by optimized material removal, to save weight and cost without imposing any general architectural constraints on the design of the flexible axle.

  It will be noted that the zone of matter between the attenuations 11 is, according to the invention, a zone of high stresses since the quantity of material transmitting the torsional forces of the antidebar 5 towards the longitudinal arm 2 is reduced. By way of non-limiting example, FIGS. 8a-8c show optimized forms of attenuation 11 taking into account the principal parameters that are, for example, the radius of curvature of the ends of the attenuation 11, the length of these attentions 11, their shape open or closed at their end. In addition, the distance between the weakens 11 and the zone on which the anti-roll bar 5 is fixed is sufficiently large for a weld bead capable of accommodating the forces passing from the anti-roll bar 5 towards the longitudinal arm 2, can be stretched on the arm 2 around the end of the bar 5. In order to allow easier welding, the lateral end 51 of the anti-roll bar 5 can penetrate into the thickness of the 2. In the case where the lateral end 51 of the anti-roll bar 5 bears on the wall 21 of the arm 2, the operator must strongly press on the anti-roll bar 5 of the anti-roll bar 5. a hand and the welding of the second hand is then more difficult to achieve.

  As represented in FIG. 8d, an asymmetry between the shape of the attenuation 11 in front of the anti-roll bar 5 and the shape of the weakening 11 behind this bar 5, due to an architectural constraint for example, It can then be compensated for, for example, by an appropriate choice of dissimilar lengths of the front and rear portions (relative to the anti-roll bar of the weakens 11, and of different openings.

Claims (10)

  1. Axle for a motor vehicle comprising two longitudinal arms (2, 3) connected transversely by at least one cross member (4) and an anti-roll bar (5), a first end (51) of the anti-roll bar (5) being made integral with one face (21i, 21e, 22i, 22e) of a first longitudinal arm 2, the second end of the anti-roll bar (5) being secured to one side of the second longitudinal arm (3) , so that the anti-roll bar (5) gives the flexible axle (1) a torsional stiffness about an axis substantially parallel to the axis of this bar (5), characterized in that one end (51) of the 1o anti-roll bar (5) is secured to the associated longitudinal arm (2) by means of an elastically deformable blade (10) so as to allow a torsion of said end of the anti-roll bar cant (5) about an axis substantially parallel to the associated longitudinal arm (2).   2. Flexible axle according to claim 1, characterized in that the elastically deformable blade (10) is a portion of said face (21i, 21e, 22i, 22e) of the longitudinal arm (2), delimited by zones of weakening. (11).   3. Flexible axle according to claim 2, characterized in that the arm (2), hollow, has at least two walls (21, 22) substantially parallel to the median plane of the vehicle, and in that the weakening zones (11 ) are made by reductions (13) of the thickness of the corresponding wall (21, 22) to said arm face (21i, 21e, 22i, 22e).   4. Flexible axle according to claim 3, characterized in that the reductions (13) are formed on the inner surface (21i, respectively 22i) of said wall (21, respectively 22).   5. Flexible axle according to claim 2, characterized in that the weakening zones (11) are constituted by through holes (12).   6. Flexible axle according to one of claims 2 to 6, characterized in that the weakening zones (11) formed in the face of the longitudinal arm (2) on which is secured the anti-roll bar (5) extend on consecutive faces of the same longitudinal arm (2).   1o 7. Flexible axle according to claim 2, characterized in that the end (51) of the anti-roll bar (5) is secured to the inner side wall (21) of the longitudinal arm (2), facing the another longitudinal arm (3), and in that the weakening zones (11) are formed in this inner side wall (21).   8. Flexible axle according to the preceding claim, characterized in that the cross member (4) is a section section "U" inside which is housed the anti-roll bar (5) and in that the zones of weakening (11) are made in the side wall (21) of the longitudinal arm (2), also within the area delimited by the profile of this cross.   9. Flexible axle according to claim 2, characterized in that the end (51) of the anti-roll bar (5) is secured to the outer side wall (22) of the longitudinal arm (2), oriented to the opposite of the other longitudinal arm (3), in that the weakening zones (11) are formed in this outer lateral wall (22), and in that an opening, the diameter of which is greater than the diameter of the anti-roll bar 5, is formed in the inner side wall (21) of the same longitudinal arm (2).   10. Flexible axle according to one of the preceding claims, characterized in that it has a general symmetry of design relative to a longitudinal and vertical median plane of the vehicle, with an elastically deformable blade (10) integral with each longitudinal arm (2, 3).