AUTOMOTIVE CROSSMEMBER SYSTEM WITH INSERTS FOR A CROSS GUIDE BAR

Description

[0001] The present invention relates to a crossmember system for a rear axle of a motor vehicle, equipped with a transverse guide bar support for this crossmember, as well as a motor vehicle comprising such a crossmember system.

[0002] A known type of vehicle rear axle, presented in particular by document FR-A1-2892974, includes a cross member guided laterally by a transverse bar, also called a "Panhard" bar, which is arranged substantially horizontally.

[0003] The guide bar, fixed by pivots on one side to the vehicle body and on the other to one end of the crossmember, provides guidance of this crossmember in the transverse direction of the vehicle during suspension travel, taking up lateral forces in particular in turns.

[0004] The guide bar should be positioned approximately horizontally so as to remain close to the horizontal direction during suspension travel. The end of the guide bar fixed to the crossmember then exhibits a substantially vertical movement, with a virtually zero horizontal component, thus ensuring good guidance of the crossmember.

[0005] For space reasons, another known type of cross member, notably described in document JP-B2-4276566, comprises a cross member with a rearward-extending sheet metal support at one end, welded to the rear face of the cross member. The end of this support receives the pivot of the transverse guide bar, which is thus slightly offset from the cross member.

[0006] However, the support made of sheet metal and welded onto the crossbar also made of sheet metal, can pose resistance problems, particularly at the weld between the support and the crossbar, in order to resist the lateral forces transmitted by the guide bar which can be significant.

[0007] The constraints of available volume under the vehicle body, and the need to position the guide bar close to the horizontal direction, may impose a certain length on the support.

[0008] In particular, a relatively long support acts as a lever arm, multiplying the transverse force from the guide bar and creating an alternating torque along the curves, which is applied to the connection between the support and the cross member. The fatigue resistance of the weld beads may be insufficient, especially for welds on a deformable cross member made of sheet metal.

[0009] To remedy this, it is known to reinforce the sheet metal of the crossmember at the point where it connects to the support, notably by adding thicknesses of sheet metal. However, this process increases the vehicle's mass and alters the torsional flexibility of this crossmember along its longitudinal axis, which is of great importance for rear axles with deformable crossmembers.

[0010] In general, the problem is to fix a support on a cross member, receiving significant lateral forces transmitted to this cross member, which may come from a transverse guide bar, or any other element such as a suspension element.

[0011] The present invention aims in particular to avoid these drawbacks of the prior art.

[0012] For this purpose, it proposes a rear axle crossmember system for motor vehicles comprising a sheet metal crossmember forming an open "U" in a section perpendicular to its length, equipped with a support designed to receive a force transmitted to this crossmember, this system being remarkable in that it comprises at least two tubular inserts passing through the crossmember, a spacer fitted into this crossmember, and screws for fixing the support to the crossmember which are fitted into these inserts.

[0013] One advantage of this crossbar system is that the screws, which can be tightened securely thanks to the spacer preventing crushing of the crossbar at the screw points, provide excellent stability to the support, enabling it to withstand significant alternating forces applied to its end. Furthermore, the inserts hold the spacer in position before the support is attached.

[0014] In particular, the support can receive the end of a transverse guide bar, applying high alternating transverse forces.

[0015] The cross-bracing system according to the invention may further comprise one or more of the following features, which may be combined with each other.

[0016] Advantageously, the spacer fitted between the two wings of the "U" section of the cross member is crossed by the tubular inserts.

[0017] In this case, the cross member advantageously has two flat surfaces, each positioned on one wing of the "U" section at the level of the spacer.

[0018] Advantageously, each tubular insert is crimped between the two outer faces of the cross member, so as to form a clamp on this cross member.

[0019] In this case, the tubular insert may have a collar at one end, and at the other end receiving the support the crimping formed in the thickness of the sheet metal of the cross member.

[0020] Advantageously, the crossmember system has two fixing screws aligned in the transverse direction of the vehicle, which is the direction perpendicular to the direction of travel of this vehicle, and each positioned on one side of the support.

[0021] In this case, advantageously the support has on each side a boss receiving a fixing screw which passes through this boss.

[0022] In particular, the cross member can be deformable, exhibiting torsional flexibility along its length.

[0023] The invention also relates to a motor vehicle equipped with a crossmember system comprising a rear axle crossmember with a support, remarkable in that this crossmember system has any one of the preceding characteristics.

[0024] In particular, the motor vehicle may include a guide bar in the transverse direction of the vehicle, fixed to the end of the support.

[0025] The invention will be better understood and other features and advantages will become more apparent upon reading the following description, given by way of example, with reference to the accompanying drawings in which: there figure 1 presents a crossmember system according to the invention for a rear axle with a deformable crossmember, which is equipped with a transverse guide bar; the figure 2 is a detailed view of the support for this crossbar; the figure 3 is a cross-sectional view of this support, along a cutting plane passing through the axis of the support's fixing screws; and the figures 4 et 5 are detailed views of the spacer inserted into the cross member under the support, presented respectively in perspective and in section along a cutting plane passing through the axis of the fixing screws.

[0026] In the description that follows, the longitudinal direction of the vehicle is defined as the direction of travel of this vehicle, along its length, and the transverse direction as the direction perpendicular to this longitudinal direction which lies in a horizontal plane.

[0027] THE figures 1, 2, 3 , 4 et 5 present a rear axle crossmember 2 formed from a sheet metal, arranged along the transverse direction of the vehicle, having a section perpendicular to its substantially constant length forming a horizontally placed "U", the opening of which is turned towards the rear.

[0028] Each end of the cross member 2 has forward an arm 4 arranged in the longitudinal direction of the vehicle, having at its front end a joint 6 mounted on an elastic block, receiving a fixing screw on the body of the vehicle arranged in the transverse direction of the vehicle.

[0029] Each end of the cross member has a vertical plate 8 receiving the hub of a rear wheel, and towards the rear a little before this end, a substantially horizontal cup 10 receiving the base of a suspension spring.

[0030] The deformable crossmember 2 exhibits a degree of torsional flexibility along its longitudinal axis to provide an anti-roll function that applies a restoring force when there are differences in suspension travel on either side of the vehicle. This flexibility, which depends on the thickness of the crossmember 2's sheet metal and its cross-sectional shape, is calculated to achieve the desired stiffness.

[0031] The cross member 2 has, on its left side, just before the attachment of the cup 10, two flat surfaces 12, each formed on a flange of its cross-section, parallel to each other. The flat surfaces 12 stop towards the rear before the edge of the flanges of the cross member 2, so as to leave a constant cross-section at this rear edge.

[0032] A vertically elongated support 14 has a flat base resting on the upper flat 12 of the cross member 2, which is tightened by two screws 28 passing through this cross member, spread apart in the transverse direction of the vehicle, and aligned along this direction.

[0033] The upper end of the support 14 has a ring 16 having an axis disposed substantially in the longitudinal direction of the vehicle, receiving a fixing screw 18 of a clevis 20 formed at the end of a transverse guide bar 22. The other end of the guide bar 22 has a ring 24 having an axis disposed in the longitudinal direction, intended to be inserted into a clevis fixed under the body of the vehicle.

[0034] In this way the cross member 2 is guided transversely by the guide bar 22 which resists transverse forces in turns, and which can follow the suspension travel thanks to its mounting with end cleats, while remaining close to the horizontal direction.

[0035] The length of the guide bar 22 gives a very small variation in the transverse distance between its ends, which maintains the geometry of the rear axle.

[0036] Each screw 28 for fixing the support 14, engaged from below, is fitted into a tubular insert 32 which is itself fitted into a hole in each flange of the cross member 2, and between these flanges into a hole in a spacer 30. The threaded upper end of each screw 28 is engaged in a tapped hole through a boss 26 arranged on each side of the support 14.

[0037] The spacer 30 has two parallel flat surfaces fitted inside the flats 12 of the cross member 2, and a contour forming two lobes each centered on a screw 28, so as to reduce its mass.

[0038] The spacer 30 maintains a spacing between the two flats 12 by presenting a high rigidity, allowing significant tightening of the screws 28 passing through the cross member 2.

[0039] Each insert 32 comprises a collar 34 extending below the lower flat 12, followed by a tubular section fitted into a hole in each flat and into a hole in the spacer 30 with a small clearance to facilitate insertion. The upper end of the insert 32 is crimped onto the upper flat 12, creating a countersink of this end into the thickness of the sheet metal around the hole in this flat.

[0040] In this way, the spacer 30 is easily inserted between the two flats 12, allowing for a small gap. Next, the two inserts 32 are inserted from below into the cross member 2, and then the upper end of these inserts is crimped by axially clamping the cross member sheets, thus eliminating this gap.

[0041] An axial clamping of the two flats 12 and the spacer 30 is obtained, between the lower collar 34 and the upper crimp, which guarantees the pressing and clamping of this assembly before the mounting of the screws 28 of the support 14. A sub-assembly ready for mounting on the vehicle is produced.

[0042] It should be noted that the tightening of all the superimposed components, including for each screw 28 the collar 34 of the insert 32, the two flats 12 of the cross member 2 and the two faces of the spacer 30, is important to ensure that the tightening torque of these screws is maintained over time.

[0043] Furthermore, after unscrewing the screws 28 in the event of after-sales intervention requiring dismantling of the support 14, the flats 12 of the cross member 2 remain tightened on the spacer 30 which facilitates reassembly.

[0044] The spacing in the transverse direction of the two screws 28 gives great lateral stability to the support 14, in the direction where it is subjected to significant stresses from the guide bar 22.

[0045] The fatigue resistance of the screws 28 can be superior to that of a weld made according to the prior art to fix the support 14 on the cross member 2, which ensures the long-term stability of this support.

[0046] Furthermore, the clamping force of the sheet metal of the flats 12 on the spacer 30 being given by the inserts 32, this force is not delivered by the screws 28 which allows them to be calculated as accurately as possible.

[0047] We thus first produce a sub-assembly formed by the cross member 2 which has received the spacer 30 held by the two inserts 32, which can be easily handled without risk of losing this spacer, which can then easily receive the support 14 by tightening the two screws 28.

[0048] The crossbeam system according to the invention allows easy and economical adaptation to different deformable crossbeams 2 having the same total height of their section, made with varying sheet thicknesses in order to adapt its torsional stiffness along its own longitudinal direction.

[0049] In this case we keep the same inserts 32 and the same screws 28, and we reduce the height of the spacer 30 according to the thickness of the sheets of the cross member 2 in order to adjust this spacer inside the cross member.

[0050] This results in a modular system which uses the same manufacturing stations with a unique and robust manufacturing process, to carry out the crimping of the inserts 32 and the screwing of the screws 28, with different sheet metal thicknesses of the cross members 2.

Claims

1. Motor vehicle rear axle cross member system comprising a cross member (2) in sheet form in a section perpendicular to its length a " U " open, equipped with a support (14) adapted to receive a force transmitted to this cross member (2), characterized in that it comprises at least two tubular inserts (32) passing through the cross member (2), a spacer (30) fitted in this cross member (2), and fixing screws (28) of the support (14) on the cross member (2) which are fitted in these inserts (32).

2. Cross member system according to claim 1, characterized in that the spacer (30) fitted between the two wings of the " U " section of the cross member (2), is traversed by the tubular inserts (32).

3. Cross member system according to claim 2, characterized in that the cross member (2) comprises two flats (12) each arranged on a wing of the " U " section at the level of the spacer (30).

4. Cross member system according to any one of the preceding claims, characterized in that each tubular insert (32) is set between the two outer faces of the sleeper (2), so as to form a clamping of the crossmember (2).

5. Cross member system according to claim 4, characterized in that the tubular insert (32) comprises at one end a flange (34), and at the other end receiving the support (14) the crimp formed in the thickness of the cross member sheet (2).

6. Cross member system according to any one of the preceding claims, characterized in that it comprises two fixing screws (28) aligned in the transverse direction of the vehicle which is the direction perpendicular to the driving direction of the vehicle and arranged each on one side of the support (14).

7. Cross member system according to claim 6, characterized in that the support (14) comprises on each side a boss (26) receiving a fastening screw (28) passing through this boss (26).

8. Cross member system according to any one of the preceding claims, characterized in that the crossmember (2) is deformable, presenting a torsional flexibility according to the a direction of its length.

9. Motor vehicle equipped with a system of cross com taking a crosspiece (2) rear axle comprising a support (14), characterized in that this system is through according to any preceding claim.

10. Motor vehicle according to claim 9, characterized in that it comprises a guide bar (22) in the transverse direction of the vehicle, fixed to the end of the support (14).