METHOD FOR ADJUSTING THE ANTI-ROLL STIFFNESS OF A SEMI-RIGID AXLE

Abstract

The invention relates to a method for adjusting the anti-roll stiffness of an axle (10) for a motor vehicle, the axle (10) comprising: - a cross member (14) with transverse axis (B) which is elastically deformable in torsion; - two generally longitudinal parallel arms (12), each intended to be connected to a body of the motor vehicle and each rigidly fixed to an outer transverse end section (24) of the cross member (14), - two gussets (26) arranged at each end section (24) of the cross member (14), each fixed to the arm (12) and to the cross member (14), and which impart to each end section (24) of the cross member (14) greater torsional stiffness contributing to the anti-roll stiffness, characterized in that the torsional stiffness of each end section (24) of the cross member (14) is adjusted by making at least one slot (40) in the corresponding gusset (26). Figure for the abbreviation: Figure 2

Description

Title of the invention: METHOD FOR ADJUSTING THE ANTI-ROLL STIFFNESS OF A SEMI-RIGID AXLE Technical field of the invention

[0001] The invention relates to a method for adjusting the anti-roll stiffness of an axle for a motor vehicle, the axle comprising:

[0002] - a transverse axis crosspiece which is elastically deformable in torsion;

[0003] - two generally longitudinal parallel arms, each of which is intended to be linked to a body of the motor vehicle and each of which is rigidly fixed to an external transverse end section of the cross member,

[0004] - two gussets arranged at each end section of the crosspiece, each of which is fixed to the arm and the cross member and which give each end section of the cross member greater torsional stiffness contributing to the anti-roll stiffness. Technical background

[0005] It is known to equip the rear axles of motor vehicles with a "semi-rigid" type axle. Such an axle mainly comprises two longitudinal arms between which extends a torsionally elastic and flexurally rigid crossmember. Each arm is connected to the crossmember by a recess-type connection.

[0006] Each arm has a front end which is pivotally mounted on the vehicle frame while a rear end carries a rear wheel of the vehicle.

[0007] The crossmember extends transversely between the two arms, offset longitudinally rearwardly relative to the front ends of the arms. The elastic properties of the crossmember enable it in particular to perform an anti-roll function which limits the rolling of the bodywork. It is, for example, known to produce tubular crossmembers from steel.

[0008] This type of axle has a small footprint and reduced mass compared to other types of axles. Such a solution is often preferred for entry-level and compact vehicles.

[0009] In certain cases this crossmember is of stamped shape with an open profile of open section evolving according to the transverse direction of the vehicle. In addition it is provided with a gusset at each end, the role of which is to contribute to the fatigue resistance of the axle, as well as to the lateral stiffness and the anti-roll stiffness of the axle.

[0010] The axle in fact allows the arms to rotate relative to each other elastically around an axis transversely, mainly by elastic torsion of the cross member. The torsional stiffness of the axle is the quantity characterizing the ratio between

[0011] - the moment to be applied to obtain an angular displacement around the axis transverse of the arms relative to each other, and

[0012] - said angular displacement.

[0013] Torsional stiffness will hereinafter be referred to as “anti-roll stiffness”, but it is also known as “anti-roll stiffness”.

[0014] The anti-roll stiffness of the axle generally depends on the model of vehicle it is fitted with. In particular, the anti-roll stiffness of the axle can vary depending on the versions of the same vehicle, in particular depending on the engine, the dimensions of the wheels or the masses of the equipment. Thus, it is common to produce cross members with profiles adapted to the desired anti-roll stiffness.

[0015] However, it would be advantageous to be able to use the same crossmember model for several vehicles requiring different anti-roll stiffnesses. This would in fact reduce production costs and the quantity of different parts to be managed. Summary of the invention

[0016] The invention proposes a method for adjusting the anti-roll stiffness of an axle for a motor vehicle, the axle comprising:

[0017] - a transverse axis crosspiece which is elastically deformable in torsion;

[0018] - two generally longitudinal parallel arms, each of which is intended to be linked to a body of the motor vehicle and each of which is rigidly fixed to an external transverse end section of the cross member,

[0019] - two gussets arranged at each end section of the crosspiece, each of which is fixed to the arm and the cross member and which give each end section of the cross member greater torsional stiffness contributing to the anti-roll stiffness,

[0020] characterized in that the torsional stiffness of each end section of the crosspiece is adjusted by making at least one slot in the corresponding gusset.

[0021] According to another characteristic of the method carried out according to the teachings of the invention, one end of the slot opens into an inner transverse end edge of the gusset.

[0022] According to another characteristic of the method carried out according to the teachings of the invention, at least one blind end of the slot does not open into a peripheral edge of the gusset.

[0023] According to another characteristic of the method carried out according to the teachings of the invention, each blind end of the slot opens into an orifice having a rounded outline to prevent cracking of the gusset.

[0024] According to another characteristic of the method carried out according to the teachings of the invention, the gusset is provided with preformed markers making it possible to determine the length of the at least one slot as a function of the desired anti-roll stiffness.

[0025] According to another characteristic of the method carried out according to the teachings of the invention, the gusset is provided with preformed markers allowing the at least one slot to be positioned according to the desired anti-roll stiffness.

[0026] According to another characteristic of the method carried out according to the teachings of the invention, the gusset is provided with preformed markers making it possible to determine the number of slots to be produced as a function of the desired anti-roll stiffness.

[0027] According to another characteristic of the method carried out according to the teachings of the invention, the markers are formed by the rounded orifices.

[0028] According to another characteristic of the method carried out according to the teachings of the invention, the markers are formed by a deformation of the gusset.

[0029] The invention also relates to an axle for a motor vehicle comprising:

[0030] - a transverse axis crosspiece which is elastically deformable in torsion;

[0031] - two generally longitudinal parallel arms, each of which is intended to be linked to a body of the motor vehicle and each of which is rigidly fixed to an external transverse end section of the cross member,

[0032] - two gussets arranged at each end section of the crosspiece, each of which is fixed to the arm and the cross member and which give each end section of the cross member greater torsional stiffness contributing to the anti-roll stiffness,

[0033] characterized in that each gusset comprises at least one slot.

[0034] According to another characteristic of the axle produced according to the teachings of the invention, one end of the slot opens into an inner transverse end edge of the gusset.

[0035] The invention also relates to a vehicle comprising an axle produced according to the teachings of the invention. Brief description of the figures

[0036] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings briefly described below.

[0037] [Fig.l] is a perspective view which represents a semi-rigid axle produced according to the teachings of the invention.

[0038] [Fig.2] is a bottom view showing the axle of [Fig.l] fitted with gussets made according to a first embodiment of the invention.

[0039] [Fig.3] is a sectional view along section plane 3-3 of [Fig.2].

[0040] [Fig.4] is a perspective view from below showing a gusset plate provided with markers according to the first embodiment of the invention.

[0041] [Fig.5] is a view similar to that of [Fig.4] which shows the gusset of [Fig.4] provided with a slot which extends to a first mark.

[0042] [Fig.6] is a view similar to that of [Fig.4] which represents the gusset of the [Fig.4] provided with a slot which extends to a second mark.

[0043] [Fig.7] is a view similar to that of [Fig.4] which shows the gusset of [Fig.4] provided with a slot which extends to a third mark.

[0044] [Fig.8] is a bottom view of a part of an axle produced according to a second embodiment of the invention equipped with a gusset comprising markers but without slots.

[0045] [Fig. 9] is a view similar to that of [Fig. 8] in which the gusset is provided with two slots made using first and second markers. Detailed description of the invention

[0046] In the remainder of the description, elements having an identical structure or similar functions will be designated by the same references.

[0047] In the remainder of the description, longitudinal, vertical and transverse orientations indicated by the trihedron "L,V,T" of the figures will be adopted, without limitation. The longitudinal direction "L" is oriented from back to front in the normal direction of movement of the vehicle. The vertical direction "V" is oriented from bottom to top from the ground on which the vehicle rests towards the roof of the vehicle.

[0048] In the following, the term “internal” will be used to designate elements located inside the profile of the cross member 14, while the term “external” will be used to designate elements located outside the profile of the cross member 14. Similarly, the term “internal” will be used to designate elements located near the middle of the cross member 14 in a transverse direction, while the term “external” will be used to designate elements located near the arms 12 of the axle 10.

[0049] [Fig.l] shows a rear axle 10 of a motor vehicle. This is an axle 10 of the "semi-rigid" type. It comprises two parallel arms 12, called longitudinal arms 12, each of which has a generally longitudinal main axis "A". The two longitudinal arms 12 are connected to each other by a cross member 14 with a transverse main axis "B".

[0050] Each longitudinal arm 12 extends from a first front end 16 to a second rear end 18. The first front end 16 is intended to be pivotally mounted about a transverse axis on a chassis (not shown) of the vehicle.

[0051] A rear end section of each longitudinal arm 12 is provided with a bracket 20 which is intended to rotatably support an associated rear wheel (not shown) of the vehicle.

[0052] In the embodiment shown in [Fig.l], the longitudinal arm 12 also comprises a cup 22 for supporting a suspension member of the vehicle. The cup 22 is here attached and fixed to the arm 12 and to the cross member 14.

[0053] The crosspiece 14 extends from a first transverse end section 24 to a second transverse end section 24.

[0054] The crosspiece 14 is here in the form of a steel tube. The crosspiece 14 has, in section along a longitudinal vertical plane, an open profile along its entire length. In the example shown in [Fig.l], the crosspiece 14 has a downwardly open profile.

[0055] The crosspiece 14 here has a “U” shaped profile. It comprises a substantially horizontal bottom 15 and two wings 17 which extend substantially vertically from two longitudinal edges of the bottom 15.

[0056] The profile of the crosspiece 14 is here substantially the same throughout the crosspiece.

[0057] Alternatively, the profile of the crosspiece 14 can be scalable in the transverse direction.

[0058] The crosspiece 14 is made so as to be rigid in bending in the vertical plane and in the longitudinal plane and so as to be flexible in torsion around its main transverse axis "B". The wall of the crosspiece 14 has a first determined thickness which allows the crosspiece 14 to have sufficient flexibility in torsion to perform its anti-roll function.

[0059] A free end of each end section 24 of the crosspiece 14 is rigidly fixed to the associated longitudinal arm 12 according to the same arrangement. Each end section 24 is fixed to the associated arm 12 by any known means, such as welding.

[0060] As is particularly visible in [Fig.2], the axle comprises two gussets 26 arranged at each end section 24 of the crossmember 14. Each gusset 26 is in the form of a sheet metal plate. By way of non-limiting example, the sheet metal plate is here shaped by stamping.

[0061] Each gusset 26 is made in a single piece. As shown in more detail in Figures 4 to 7, each gusset 26 here has the shape of a generally rectangular plate which extends in a transverse direction from an outer end edge 28, arranged close to the associated arm 12, to an opposite inner end edge 30. Each end edge 28, 30 extends longitudinally. In addition, each gusset 26 is delimited longitudinally by two lateral edges 32 which extend transversely. Each lateral edge 32 here comprises a rim which extends vertically downwards.

[0062] As shown in [Fig. 4], each gusset 26 has an outer end portion 34 that extends horizontally, while an inner end portion 36 is inclined upwardly relative to a horizontal plane. The outer end portion 34 and the inner end portion 36 are connected by a fold 38 with a longitudinal axis.

[0063] Each gusset 26 has the function of contributing to the fatigue resistance of the axle 10, in particular to guarantee good resistance of the arms 12 on the cross member 14. In addition, each gusset 26 helps to provide greater anti-roll stiffness to the axle 10, particularly at the end sections 24 of the crossmember 14.

[0064] To do this, the gussets 26 are positioned from below inside the end sections 24 of the crosspiece 14 to close the profile near the arms 12, as shown in [Fig.3].

[0065] In this position, the lateral edges 32 of the gussets 26 shown in the figures are in contact with an internal face of the wings 17 of the crosspiece 14. The inner end edge 30 is in contact with the internal face of the bottom 15, while the outer end edge 28 is in contact with a face of the associated arm 12.

[0066] Each gusset 26 is then attached to the arm 12 and to the cross member 14. For example, the outer end edge 28 is attached by welding to the arm 12, while the inner end edge 30 is attached by welding to the cross member 14.

[0067] Optionally, the two lateral edges 32 can be fixed to the wings 17 of the crosspiece 14, for example by welding.

[0068] Each gusset 26 has a transverse length which is less than or equal to half the transverse length of the crosspiece 14. Each gusset 26 is here shorter than half the transverse length of the crosspiece 14 so that there remains a central section of the crosspiece 14, located between the two end sections 24, the profile of which remains open after arrangement of the gussets 26.

[0069] The value of the anti-roll stiffness of the axle 10 may vary depending on the versions of the same vehicle (engine, wheel dimensions, mass of the equipment) or from one vehicle model to another.

[0070] To optimize the manufacturing cost and reduce the number of parts to be managed, the invention proposes using identical components, in particular identical cross members 14 and identical gussets 26, to produce axles 10 having different anti-roll stiffnesses.

[0071] To do this, the invention proposes a method for adjusting the anti-roll stiffness of the axle 10 in which the torsional stiffness of the ends of the crossmember 14 is adjusted by making at least one slot 40 in the corresponding gusset 26. Thus, from the same gusset 26, it is possible to obtain several different anti-roll stiffnesses.

[0072] According to a first embodiment of the invention shown in Figures 2, 3 and 5 to 7, each gusset 26 comprises a single slot 40, one end of which opens into the inner transverse end edge 30 of the gusset 26. The other end of the slot is blind, that is to say it does not open into a peripheral edge of the gusset 26. Thus, an inner end section 42 of the gusset 26 is split into two tabs 45, while an outer end section 44 of the gusset 26 is not split.

[0073] The slot 40 is rectilinear. The slot 40 extends here transversely. The slot 40 extends here in the inner end portion 36 of the gusset 26.

[0074] Thus, when the cross member 14 works in torsion around its transverse axis “B”, the split section 42 does not substantially oppose the torsion, because the two tabs 45 on either side of the slot 40 can deform elastically with a large amplitude. Only the non-split section 44 of the gusset 26 has a stiffness which contributes to the anti-roll stiffness. Thus, the longer the slot 40, the lower the anti-roll stiffness of the axle 10 will be.

[0075] To prevent the blind end of the slot 40 from causing the gusset 26 to start cracking, which would be likely to propagate into the unsplit section 44, the gusset 26 comprises means for preventing the propagation of cracks. For this purpose, the blind end of the slot 40 opens here into an orifice 46 having a rounded contour. More particularly, the orifice 46 perforates the sheet metal forming the gusset 26. The orifice 46 has dimensions greater than that of the width of the slot 40. Such an orifice 46 makes it possible to avoid excessive stress concentration at the blind end of the slot 40. The orifice 46 has, for example, a circular contour and it has a diameter greater than the width of the slot 40.

[0076] In a variant not shown, the gusset may have an excess thickness at the blind end of the slot 40 to reinforce its resistance to stresses at this location.

[0077] [Fig. 4] shows a gusset 26 in which no slot 40 has yet been made. To facilitate the adjustment of the anti-roll stiffness of the axle 10 by means of the gussets 26, each gusset 26 is provided with preformed marks allowing an operator to determine the length of the slot 40 as a function of the desired anti-roll stiffness. These marks also allow the slot 40 to be correctly positioned on the gusset 26.

[0078] The marks are here formed by rounded orifices 46A, 46B, 46C which are intended to form the means for preventing the propagation of cracks. The gusset 26 shown in [Fig.4] thus comprises several orifices 46A, 46B, 46C which are aligned transversely at a distance from each other, here three orifices 46A, 46B, 46C. They are arranged substantially in the middle of the gusset 26 in a longitudinal direction.

[0079] Thus, when it is desired to obtain a crosspiece 14 having a first predetermined anti-roll stiffness, no slot 40 is made, as shown in [Fig.4].

[0080] To obtain a second predetermined anti-roll stiffness which is less than the first anti-roll stiffness, the slot 40 is made from the inner end edge 30 to the first orifice 46A located closest, as shown in [Fig.5].

[0081] To obtain a third predetermined anti-roll stiffness which is less than the second anti-roll stiffness, the slot 40 is made from the inner end edge 30 to the second orifice 46B starting from the inner end edge 30, as shown in [Fig.6]. The slot 40 then passes through the first orifice 46A.

[0082] To obtain a fourth predetermined anti-roll stiffness which is less than the third anti-roll stiffness, the slot 40 is made from the inner end edge 30 to the third orifice 46C starting from the inner end edge 30, as shown in [Fig.7]. The slot 40 then passes through the first orifice 46A and the second orifice 46B.

[0083] This arrangement allows an operator to quickly produce the gusset 26 having the desired anti-roll stiffness while minimizing the risk of errors.

[0084] In a variant of the invention not shown, the markers may be formed by a local deformation of the gusset 26, for example by a depression.

[0085] During the manufacture of the axle 10, the gusset 26 without slot 40, as shown in [Fig. 4], is first manufactured. Advantageously, the marks, here the orifices 46A, 46B, 46C are made in the gusset 26, for example by drilling or perforation.

[0086] Before positioning the gusset 26 in the crosspiece 14, the gusset 26, previously provided with its marks, is prepared according to the anti-roll stiffness sought for the crosspiece 14. If necessary, the slot 40 is then made to the desired length. The slot 40 is for example made by cutting.

[0087] The gusset 26 is then positioned in the crosspiece 14, previously mounted with the rest of the axle 10. Then the gusset 26 is fixed, for example by welding.

[0088] According to an alternative embodiment of the invention shown in Figures 8 and 9, the anti-roll stiffness of the axle 10 is adjusted by producing in the gusset 26 at least one slot 40A having two blind ends. The slot 40 thus does not open into any of the peripheral edges of the gusset 26.

[0089] Each slot here has a chevron shape whose point is directed transversely outwards. Each blind end of the slot 40A is then provided with means to prevent the propagation of the figures.

[0090] These means are similar or identical to those described for the first embodiment. Thus, each blind end of the chevron-shaped slot 40A opens into an associated orifice 46A.

[0091] Furthermore, the slot 40 having a non-rectilinear shape having an angle, here at the tip of the chevron, said angle is also likely to form an initiation of cracking. The tip of the chevron is therefore also provided with a means for preventing the propagation of cracks, here formed by an associated orifice 46A.

[0092] As explained in the first, each gusset 26 is advantageously provided with preformed markers making it possible to produce the number of slots as a function of the stiffness desired anti-roll stiffness. These markers also allow at least one slot to be positioned according to the desired anti-roll stiffness.

[0093] As in the first embodiment, the marks are here formed by rounded orifices 46A, 46B, 46C which are intended to form the means for preventing the propagation of cracks. The gusset 26 shown in [Fig.8] thus comprises three orifices 46A forming a first chevron, three orifices 46B forming a second chevron, and three orifices 46C forming a third chevron. The chevrons are aligned transversely at a distance from each other. They are arranged substantially in the middle of the gusset 26 in a longitudinal direction.

[0094] In a variant of the invention not shown, the markers are formed by a deformation of the gusset 26.

[0095] The axle 10 is manufactured as for the first embodiment with the difference that several slots 40A, 40B may be made, as shown in [Fig.9], before the gusset 26 is mounted in the crosspiece 14.

[0096] The invention thus makes it possible to produce axles 10 having different anti-roll stiffnesses from the same components and in particular from the same crossmember 14 and the same gussets 26. A simple operation of cutting out slots 40 makes it possible to obtain the desired anti-roll stiffness.

[0097] Advantageously, the number and / or the position and / or the length of the slots are chosen as a function of the targeted anti-roll stiffness. Preferably, these anti-roll stiffnesses are predetermined and the gussets have markers to facilitate the production of these predetermined anti-roll stiffnesses.

Claims

Claims

1. Method for adjusting the anti-roll stiffness of an axle (10) for a motor vehicle, the axle (10) comprising: - a cross member (14) with a transverse axis (B) which is elastically deformable in torsion; - two generally longitudinal parallel arms (12), each of which is intended to be connected to a body of the motor vehicle and each of which is rigidly fixed to an outer transverse end section (24) of the crossmember (14), - two gussets (26) arranged at each end section (24) of the crossmember (14), each of which is fixed to the arm (12) and to the crossmember (14) and which give each end section (24) of the crossmember (14) greater torsional stiffness contributing to the anti-roll stiffness, characterized in that the torsional stiffness of each end section (24) of the crossmember (14) is adjusted by making at least one slot (40) in the corresponding gusset (26).

2. Method according to the preceding claim, characterized in that one end of the slot (40) opens into an inner transverse end edge (30) of the gusset (26).

3. Method according to any one of the preceding claims, characterized in that at least one blind end of the slot (40) does not open into a peripheral edge of the gusset (26).

4. Method according to the preceding claim, characterized in that each blind end of the slot (40) opens into an orifice (46A, 46B, 46C) having a rounded outline to prevent cracking of the gusset (26).

5. Method according to any one of the preceding claims, characterized in that the gusset (26) is provided with preformed marks making it possible to determine the length of the at least one slot (40) as a function of the desired anti-roll stiffness.

6. Method according to any one of the preceding claims, characterized in that the gusset (26) is provided with preformed markers making it possible to position the at least one slot (40) according to the desired anti-roll stiffness.

7. Method according to any one of the preceding claims, characterized in that the gusset (26) is provided with preformed marks making it possible to determine the number of slots (40A, 40B) to be made in function of the desired anti-roll stiffness.

8. Method according to any one of claims 5 to 7 taken in combination with claim 4, characterized in that the marks are formed by the rounded orifices (46A, 46B, 46C).

9. Method according to any one of claims 5 to 7, characterized in that the marks are formed by a deformation of the gusset (26).

10. Axle (10) for a motor vehicle comprising: - a cross member (14) with a transverse axis (B) which is elastically deformable in torsion; - two generally longitudinal parallel arms (12), each of which is intended to be connected to a body of the motor vehicle and each of which is rigidly fixed to an outer transverse end section (24) of the cross member (14), - two gussets (26) arranged at each end section (24) of the cross member (14), each of which is fixed to the arm (12) and to the cross member (14) and which give each end section (24) of the cross member (14) greater torsional stiffness contributing to the anti-roll stiffness, characterized in that each gusset (26) comprises at least one slot (40).

11. Axle (10) according to the preceding claim, characterized in that one end of the slot (40) opens into an inner transverse end edge (30) of the gusset (26).

12. Vehicle comprising an axle (10) made according to any one of the preceding claims.

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