EP1654130A1

EP1654130A1 - Flexible axle for a motor vehicle

Info

Publication number: EP1654130A1
Application number: EP04767502A
Authority: EP
Inventors: Laurent Taupin
Original assignee: Auto Chassis International SNC
Current assignee: Auto Chassis International SNC
Priority date: 2003-08-08
Filing date: 2004-06-29
Publication date: 2006-05-10
Also published as: KR20060037429A; WO2005023570A1; FR2858585A1; FR2858585B1; JP2007501728A

Abstract

The inventive axle for a motor vehicle comprises two longitudinal arms (2, 3) which a transversally connected by means of at least one crossbar and an anti-overturning bar (5), the first end (51) of said anti-overturning bar (5) being connected to the face (21i, 21e, 22i, 22e) of the first longitudinal arm (2) and the second end thereof being connected to the face of the second longitudinal arm (3) in such a way that the anti-overturning bar (5) confers to a flexible axle (1) a torsional rigidity around an axis which is substantially parallel to the axis thereof. Said invention is characterised in that the end (51) of the anti-overturning bar (5) is connected to the associated longitudinal arm (2) by means of an elastically deformable blade (10) in such a way that said end of the anti-overturning bar (5) is enabled to twist around an axis which is substentially parallel to the associated longitudinal arm (2), said elastically deformable blade (10) being embodied in the form of a part of said face (21i, 21e, 22i, 22e) of the first longitudinal arm (2) limited by weaken areas (11).

Description

FLEXIBLE AXLE FOR MOTOR VEHICLE E

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 made integral with one face of a first longitudinal arm, the second end of the anti-roll bar being made integral with one face of the second longitudinal arm, so that the anti-roll bar gives the flexible axle torsional rigidity around 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, essentially by assemblies of the mechanically welded type, have caused a significant deployment of the flexible axle technique by the manufacturers. automobiles.

Flexible axles are thus used on all types of vehicle and increasingly on heavy vehicles, for which multi-link trains were previously preferred. In this type of vehicle (large sedan, minivan or even utility vehicle), certain elements of the anti-roll bar are close to their absolute operating limits, due to the large mass of the vehicle and the concern for optimal performance. However, the anti-roll bar is one of the most delicate 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, which are generally welded, are particularly stressed and require the full attention of the designers, otherwise the connection will break prematurely.

Certain solutions have been applied to flexible axles in the past in order to improve the endurance resistance of this connection. These solutions revolve around the observation that during a cant loading, in addition to the expected torsional stress, the anti-tilt bar is also subjected to a significant bending tending to deform it in "S" in a vertical plane. This stress has no functional value and has a preponderant influence on the resistance of the weld beads between the anti-roll bar and the longitudinal arms. The document FR-A-2795681 describes and represents an anti-roll bar with an oblong section in order to reduce the share of flexion in cant in the overall stress. However, this technique is limited by manufacturing constraints, the flattening of the anti-roll bar cannot in fact exceed a critical value beyond which cracks start inside the bar and clearly degrade its performance. endurance.

One of the objectives of the invention is therefore to propose a flexible axle making it possible to reduce the part of the anti-roll bar's cantilever bending relative to a transverse axis of the vehicle, without however reducing its main torsional benefits around the same transverse axis. According to the objectives specific to each manufacturer, the flexible axle must also be compact, inexpensive and easy to integrate into the environment of the vehicle.

To meet these objectives, the invention provides a flexible axle of the type described above, characterized in that one end of the anti-roll bar cant is made integral with the associated longitudinal arm by means of an elastically deformable blade so as to allow torsion of said end of the anti-roll bar around 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 intermediate parts, and therefore of weight. In addition, the fact that the deformable blade is a portion of the face of the arm allows this blade to be installed on any type of longitudinal arm, whatever the general architecture of the associated suspension train of the vehicle.

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

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

According to a characteristic of the invention, the weakening zones produced in the face of the longitudinal arm on which the anti-roll bar is secured are extended on other faces of the same longitudinal arm.

According to a 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 produced in this inner lateral face.

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

According to a characteristic of the invention, the end of the anti-roll bar is made integral with the external lateral face of the longitudinal arm, oriented opposite the other longitudinal arm, and the weakening zones are produced in this outer lateral face, and in the inner lateral face of the same longitudinal arm.

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

Other characteristics 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: - Figure 1 is a schematic representation of a flexible axle according to invention, - Figure 2 is a schematic representation of the principle of the invention, - Figure 3 is a perspective view of a flexible axle according to the invention according to a first embodiment, - Figure 3a is a section of the flexible axle shown in Figure 3, along a vertical plane and in the axis of the anti-roll bar. - Figure 4 is a view similar to that of Figure 3 according to a second embodiment, - Figure 4a is a section of the flexible axle shown in Figure 4, along a vertical plane and in the axis of the anti-roll bar. - Figure 4b is a section similar to that of Figure 4a, according to an alternative embodiment of the invention, - Figure 5 is a section of the flexible axle according to a first variant of. second embodiment, along 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 FIG. 3 according to a third variant of the second embodiment, - FIGS. 8a, 8b ₅ 8c and 8d are schematic representations of different design variants of the weakening zones according to the invention.

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

As shown in FIG. 1, a flexible rear axle 1 consists of two longitudinal arms 2 and 3, connected by a front cross member 4. Advantageously, the longitudinal arms have the form 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 however be understood that the present invention can be applied to other arm shapes. Parallel to the cross-member 4, a rear anti-roll bar 5 extends from one longitudinal arm 2 to the other 3. Such a flexible axle 1 having 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 below 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 articulated under the body of the vehicle by means of a bearing 6 and the rear end of this 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 depending on the architecture of the suspension train of the vehicle and the desired performance for the anti-roll bar 5, it can be envisaged, as shown in FIG. 5, to have a bar length such that this one must be welded to the external lateral 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 certain flexibility in torsion around a substantially longitudinal axis. A schematic diagram of the behavior of this blade 10, when the vehicle is loaded on a slope, is thus represented in FIG. 2. According to a first embodiment, of the type shown in FIG. 3, the weakenings 11 are through holes 12 located in the side wall 21 on which the anti-roll bar 5 is welded. A second embodiment of these weakenings 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 reductions 13 in thickness made in the internal side wall 21, on the external face 21e of this wall 21. Such an embodiment by reductions 13 in thickness makes it possible not to create openings 12 in the arms 2 and not to have to take care of the sealing of the through holes 12 for sealing or corrosion issues. Thus, it will be noted that the embodiment in which the weakenings 11 are obtained by through holes 12 should preferably be accompanied, after the welding of the end 51 of the anti-roll bar 5 on the arm 2, d '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 can be made in the internal face 21i of this wall 21. This variant embodiment, shown in FIG. 4b, also has the advantage of '' allow welding seams around the thicker anti-roll bar 5. An alternative embodiment, not shown, to obtain these thicker weld beads is to make the thickness reductions 13 in the external face 21e of the wall 21, and to weld the bar 5 on the internal face 21i. In this case, the longitudinal arm 2 will be made in 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 external lateral wall 22 of the arm 2, and therefore of an anti-roll bar 5 "transversely" crossing the longitudinal arm 2, weakenings 11 are produced jointly in the wall side wall 22. However, the side wall inner 21 must be able to accompany the torsional movement of the anti-roll bar 5 around a substantially longitudinal axis, movement authorized by the elastically deformable blade 10 formed in the outer side wall 22. As shown in FIG. 5, the wall inner lateral 21 must therefore have an opening whose diameter is sufficient to allow the deflection 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 is the cross member 4. According to the arrangements made on the rear axle of the vehicle, and according to the shape of the cross member 4, the anti-roll bar cant 5 can then be housed inside the cross-member 4 (FIG. 6 represents such a train architecture, with a cross-member in “U” profile). In this case, the resiliently deformable blade 10 must be produced only in the side walls, interior 21 if the anti-roll bar 5 is welded to the internal side wall 21, or external 22 if the anti-roll bar 5 is welded to the external 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 weakenings 11 made in several consecutive faces. In this case, shown in Figure 7, the main direction of weakening 11 must remain in a substantially longitudinal direction, to allow the torsion of the anti-roll bar 5 around an axis in this direction.

The working zone between the weakenings 11 combines good torsional flexibility around the longitudinal axis of the vehicle, and great torsional stiffness around the transverse direction. It therefore responds directly to the various objectives of the invention set out above, since it considerably limits the harmful effects of bending without affecting the torsion of the anti-roll bar 5 which is practically entirely transmitted. The various embodiments of the invention allow, by the optimized removal of material, a saving in mass and cost without imposing general architectural constraints on the design of the flexible axle.

It will be noted that the area of material between the weakenings 11 is, according to the invention, an area of high stresses since the amount of material transmitting the torsional forces of the anti-roll bar 5 towards the longitudinal arm 2 is reduced. By way of non-limiting example, FIGS. 8a to 8c show optimized forms of weakening 11 taking into account the main parameters such as the radius of curvature of the ends of the weakening 11, the length of these weakenings 11, their open shape or closed at their end. In addition, the distance between the weakenings 11 and the area on which the anti-roll bar 5 is fixed is large enough for a weld bead, capable of absorbing the forces passing from the anti-roll bar 5 towards the arm. longitudinal 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 the thickness of the wall 21 of the longitudinal arm 2.

As shown in FIG. 8d, an asymmetry between the form of the weakening 11 in front of the anti-roll bar 5 and the form of the weakening 11 behind this bar 5, due to an architectural constraint for example, could then be compensated, for example by an appropriate choice of dissimilar lengths of the front and rear parts (relative to the anti-roll bar 5) of the weakenings 11, and of different openings.

Claims

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 a face (21i, 21e, 22i, 22e) of a first longitudinal arm 2, the second end of the anti-roll bar (5) being made integral with a face of the second longitudinal arm (3 ), so that the anti-roll bar (5) gives the flexible axle (1) torsional rigidity around an axis substantially parallel to the axis of this bar (5), characterized in that end (51) of the anti-roll bar (5) is made integral with the associated longitudinal arm (2) by means of an elastically deformable blade (10) so as to allow torsion of said end of the anti-roll bar cant (5) around 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 weakening zones (11).

3. Flexible axle according to claim 2, characterized in that the hollow arm (2) has at least two walls (21, 22) substantially parallel to the median plane of the vehicle, and in that the weakening zones (11 ) are produced by reductions (13) in the thickness of the corresponding wall (21, 22) on said face of the arm (21i, 21e, 22i, 22e).

4. Flexible axle according to claim 3, characterized in that the reductions (13) are carried out on the internal surface (21i, respectively 22i) of said wall (21, respectively 22).

5. Flexible axle according to claim 2, characterized in that the weakened zones (11) consist of 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 the anti-roll bar (5) is secured are extended on consecutive faces of the same longitudinal arm (2).

7. Flexible axle according to claim 2, characterized in that the end (51) of the anti-roll bar (5) is made integral with the inner side wall (21) of the longitudinal arm (2), oriented towards other 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 with a "U" section inside which the anti-roll bar (5) is housed and in that the zones of weakenings (11) are carried out in the side wall (21) of the longitudinal arm (2), also inside the zone delimited by the profile of this crosspiece.

9. Flexible axle according to claim 2, characterized in that the end (51) of the anti-roll bar (5) is made integral with the outer side wall (22) of the longitudinal arm (2), oriented at opposite the other longitudinal arm (3), in that the weakening zones (11) are produced in this outer side wall (22), and in that an opening, the diameter of which is greater than the diameter of the anti-roll bar 5, is made 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 with respect to a longitudinal and vertical median plane of the vehicle, with an elastically deformable blade (10) secured to each longitudinal arm ( 2, 3).