FR2832099A1 - Multi-arm rear wheel axle unit comprises, for each wheel, rear and front transverse arms pivoted by elastic connections to chassis and to wheel pivot and omega shaped suspension spring - Google Patents

Abstract

The rear wheel axle unit comprises, for each wheel, two front (2) and rear (4) transverse arms and a longitudinal arm pivoted by elastic connections to the vehicle chassis (8) at one of their ends and to the wheel pivot (10) at their opposite ends. There is an omega shaped suspension spring (13) and damper (12) which comprises a rod (12a)) connected to the chassis by an elastic connection and a body (12b) fixed to the wheel pivot.

Description

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 The present invention relates generally to the rear axles of motor vehicles.

 More specifically, the invention relates to a rear axle of a motor vehicle comprising, for each wheel, two front and rear transverse arms and a longitudinal arm, pivotally mounted by elastic connections to the chassis of the vehicle at one of their ends and to the pivot. wheel at their opposite ends, a shock absorber which comprises a rod connected to the chassis by an elastic connection and a body integral with the wheel pivot, and a suspension spring.

 Rear axles of this type are known from the prior art, in particular by French patent application 2 788 473 describing a system in which the helical suspension spring is not coaxial with the shock absorber and is supported at its lower part on a support connecting the two transverse arms. The support extends substantially longitudinally with respect to the vehicle and comprises two cylindrical end parts fixed respectively to the two transverse arms by means of elastic joints. The suspension spring bears on its upper part on the chassis of the vehicle.

 It is also known that the wheel pivots commonly used in the rear axles of motor vehicles have complex shapes due to their multiple connections with other parts of the vehicle, and are generally foundry parts.

 The trains known from the prior art are therefore ill-suited to countries with a low technological level. They have complex and fragile connections, in particular between the spring support and the transverse bars, which require qualified technical personnel for maintenance. Furthermore, foundry parts are expensive and require significant infrastructure for their production. Mechanical parts

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 welded can be produced very easily, in small workshops equipped with limited means.

 The purpose of the present invention is therefore to provide a simple rear axle, well suited to developing countries, or more generally to countries where the general technical level is not very high, but retaining the interesting characteristics of the trains described. in the preamble, namely being able to be self-tugging if the transverse bars are of different lengths, and allowing a saving of space compared to conventional trains with helical spring wound around the shock absorber, which makes it possible to increase the volume of the boot.

 This rear axle must be able to be installed on rear-wheel drive vehicles, such as 4x4s.

 To this end, the rear axle of the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the wheel pivot is in the general form of a box with welded sheet plates crossed by the lower part of the damper body rigidly fixed by welding to the box.

 In a possible embodiment of the invention, the pivot can comprise a central box, a front box to which the shock absorber body is welded and a shoe on which are mounted by elastic pivot connections the transverse arms, the longitudinal arm and the suspension spring, the front box and the shoe being rigidly connected by welding to the central box.

 Advantageously, the front box can include an upper plate and a lower plate connected by at least one side plate, the lower part of the damper body passing through the upper plate and the lower plate along a substantially vertical axis and being welded to these upper plates. and lower.

 Preferably, the shoe can include a bottom plate and at least two vertical edges before and

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 rear substantially transverse, the front and rear transverse arms being respectively connected by one of their elastic connections to the front and rear edges, the longitudinal arm and the suspension spring being linked by one of their elastic connections to the bottom plate .

 For example, the central box can comprise two transverse front and rear lateral plates connected by at least one lateral link plate on the wheel side to which a wheel stub axle is fixed, and by a bottom plate, the central box being at less partially engaged in the hoof and resting by its bottom plate on the hoof bottom plate.

 Advantageously, the suspension spring can have the general shape of a Q, one end of the spring being linked to the chassis by an elastic pivot connection around a transverse axis, an opposite end being linked to the pivot by an elastic pivot connection around 'another axis.

 Preferably, the bottom plate can carry, on its lower face, at least of the first and second stirrups, one end of the longitudinal arm coming to articulate in the first stirrup, and one end of the suspension spring coming to articulate in the second stirrup.

 For example, the axes of the pivot connections of the ends of the suspension spring may lie in the same vertical vertical plane of the front and rear transverse side plates of the central box.

 Advantageously, the front box can be welded to an external face of the front transverse plate of the central box.

 Preferably, the central box can have the general shape of a rectangular parallelepiped whose side face opposite the wheel comprises at least one recessed area.

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 For example, a drive shaft can pass through the central box passing through said recessed area, the drive shaft being engaged by one end in the center of the wheel stub axle.

 Advantageously, the axis of the drive shaft can be located in the median plane of the front and rear transverse plates.

 Preferably, a square piece can be rigidly connected to the central box on the side opposite the wheel, in the extension of the angle between the bottom plate of the central box and the front side plate of this box, an axis of the connection pivot of the front transverse arm passing through both the front edge of the shoe and the angle piece.

- la figure 2 est une vue de dessus correspondant à la figure 1, - la figure 3 est une vue de côté suivant la flèche III de la figure 1, - la figure 4 est une vue en perspective du pivot de roue des figures précédentes, - la figure 5 est une vue schématique arrière représentant la cinématique de fonctionnement du train arrière de l'invention ; et - la figure 6 est une vue schématique de dessus suivant la flèche VI de la figure 5. Other characteristics and advantages of the invention will emerge clearly from the description given below, by way of indication and in no way limiting, with reference to the appended drawings, in which: - Figure 1 is a rear view of a side of a rear axle according to the invention,

- Figure 2 is a top view corresponding to Figure 1, - Figure 3 is a side view along arrow III of Figure 1, - Figure 4 is a perspective view of the wheel pivot of the previous figures, - Figure 5 is a schematic rear view showing the operating kinematics of the rear axle of the invention; and - Figure 6 is a schematic top view along arrow VI of Figure 5.

 FIGS. 1 to 3 represent a side of a rear undercarriage of a motor vehicle of the type comprising, for each wheel, two parallel transverse arms front 2 and rear 4, and a longitudinal arm 6.

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 These arms 2,4 and 6 are pivotally mounted by elastic connections to the chassis 8 of the vehicle at one of their ends and to the pivot 10 carrying the wheel at their opposite ends. The rear axle also comprises a shock absorber 12 which extends in a substantially vertical direction and which comprises a rod 12a connected to the chassis 8 by an elastic connection and a body 12b secured to the pivot 10, and a suspension spring 13.

 According to the invention, the pivot 10 is in the general form of a box constructed of welded sheets.

 More precisely, this pivot 10 comprises a central box 14, a front box 16 to which the shock absorber body 12b is welded and a shoe 18 on which are mounted by elastic pivot links the front 2 and rear 4 transverse arms, the longitudinal arm 6 and the suspension spring 13. The front box 16 and the shoe 18 are rigidly connected by welding to the central box 14.

 Other types of connections between the different elements of the pivot 10 are possible, such as by screwing or riveting.

 As can be seen in Figure 4, the front box 16 comprises an upper plate 16a and a lower plate 16b connected by at least one side plate 16c. In the embodiment illustrated in FIG. 4, the upper plate 16a and the lower plate 16b are substantially horizontal, rectangular and parallel. The side plate 16c is vertical and substantially transverse. The longitudinal faces are shown hollowed out in FIG. 4 but can also be formed by welded plates, for example at the upper, lower and lateral plates 16a, 16b, 16c.

 The lower part 12c of the damper body 12b passes through the upper plate 16a and the lower plate 16b along an axis generally inclined by a few

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 degrees from the vertical. This lower part 12c is fixed to the upper plate 16a and to the lower plate 16b by welding, generally over the entire perimeter of the intersections between this lower part 12c and the plates.

 The shoe 18 comprises a bottom plate 18a, two vertical front and rear edges 18b and 18c substantially transverse and a longitudinal edge 18d on the side opposite the wheel. Shoe 18 is open on the wheel side. The front and rear vertical flanges 18b and 18c have a horizontal profile on the wheel side, which lowers towards the bottom plate 18a on the side opposite the wheel.

 The central box 14 has the general shape of a rectangular parallelepiped whose side face opposite to the wheel 14f is hollowed out.

 This central box 14 comprises two transverse front and rear lateral plates 14a and 14b connected by a lateral connection plate 14c on the wheel side, by an upper plate 14d and by a bottom plate 14e.

 A wheel stub axle 20 is rigidly fixed on the lateral connection plate 14c. This ported hub 20 protrudes towards the outside of the vehicle and is provided with a flange 22 receiving the braking system of the wheel.

 The central box 14 is partially engaged in the shoe 18. This central box 14 protrudes from the shoe 18 on the wheel side, the shoe 18 being open on this side as described above. The central box 14 rests by its bottom plate 14e on the bottom plate 18a of the shoe 18. The front side plate 14a comes into contact with the front edge 18b and the rear side plate 14b comes into contact with the rear edge 18c.

 A square piece 24 is rigidly connected to the central box 14 on the side opposite the wheel, for example by welding, in the extension of the angle between the bottom plate 14e and the front side plate 14a. The

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 angle piece 24 comprises a horizontal triangular plate 24a linked by its base to the bottom plate 14e of the central box 14, and a vertical rectangular plate 24b linked by a vertical edge to the front side plate 14a and by a horizontal edge lower than the triangular plate 24a.

 The rectangular plate 24b comes into contact with the inner face of the front edge 18b.

 It should be noted that the bottom plate 14e of the central box 14 only partially covers the bottom plate 18a of the shoe 18, the face opposite to the wheel 14f of the box 14 not arriving at the longitudinal edge 18d of the shoe 18 .

 The front box 16 is welded to an external face of the front transverse plate 14a, so that the upper plate 16a of the front box 16 is substantially in the extension of the upper plate 14d of the central box 14.

 The bottom plate 18a of the shoe 18 carries, on its underside, at least first and second vertical stirrups 26 and 28 crossed by a single transverse axis 30.

 The part of the axis 30 passing through the first stirrup 26 is surrounded by an elastic sleeve 32, around which is articulated one end of the longitudinal arm 6 consisting of a metal sheath.

 At an opposite end, the longitudinal arm 6 of the rear axle is fixed by an elastic articulation 34 to a support 36 integral with the chassis 8 of the vehicle.

 The suspension spring 13 is a leaf spring of composite material, having the general shape of a Q situated in a longitudinal vertical plane. One end of the suspension spring 13 is articulated in the stirrup 28 by a pivot connection around the axis 30, an opposite end comes to be articulated in a stirrup 38 secured to the chassis 8 of the vehicle by another pivot connection around an axis 31.

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 The part of the axis 30 passing through the stirrup 28 is surrounded by a metal sleeve 40, itself surrounded by an elastic sleeve 42. The end of the spring 13 has a shape curved towards the outside of the Q and comes be housed in the stirrup 28 around the elastic sleeve 42.

 The pivot connection of the opposite end of the spring 13 in the stirrup 38 is identical.

 The axes 30 and 31 of the pivot connections of the ends of the suspension spring 13 are located in a vertical, median plane of the front and rear transverse side plates 14a and 14b of the central box 14.

 Other materials can be used for the suspension spring 13, such as metallic materials.

 The two transverse arms 2,4 have their ends opposite the wheel articulated around a common axis 44 extending longitudinally with respect to the vehicle along the axis XX ′ and fixed to an axle crosspiece 46 by the intermediate of two elastic rubber articulation sleeves 48. The arms 2 and 4 are connected to the external faces respectively of the front edges 18b and rear 18c of the shoe 18 by means of elastic joints 50, whose respective axes 52 and 54 are parallel to the pivot axis XX 'of the two arms. The front arm 2 is shorter than the rear arm 4.

 The axis 54, in a possible embodiment of the invention, may consist of a screw passing through the rear transverse plate 14b and the rear flange 18c, the head of the screw being located inside the central box 14 .

 Likewise, the axis 52 may consist of a screw passing through the rectangular plate 24b of the bracket 24 and the front edge 18b, the head of the screw being located inside the shoe 18.

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 A drive shaft 56 passes through the central box 14 passing through the face opposite to the hollowed-out wheel 14f, to come to engage at one end in the center of the wheel stub axle 20.

 The axis of the drive shaft 56 is located substantially in the median plane of the front and rear transverse plates 14a and 14b.

 An anti-roll bar 58 is connected to the body of the shock absorber 12b by means of a link 60, this anti-roll bar 58 being articulated in a bearing 62 fixed to the chassis 8 of the vehicle.

 The operating kinematics of the rear axle described above will now be explained in conjunction with FIGS. 5 and 6.

 When the vehicle is traveling in a right turn, the left rear axle assembly shown in FIGS. 1 to 4 enters a so-called attack phase and deforms according to the kinematics specific to this axle. More particularly, the two arms of different lengths 2.4 allow, by their elastic articulations during the attack phase, that is to say when the axle rotates around the axis XX 'while moving towards the top as shown in Figure 5 while keeping the wheel axis Z-Zl in a plane parallel to the ground, a rotation of the wheel plane P towards the interior of the vehicle, thus determining a toe-in angle Q as shown in Figure 6 to allow the vehicle to adopt understeer behavior, thereby promoting vehicle handling.

 The possibility of keeping the wheel axle Z-21 in a plane parallel to the ground during the geometric deformation of the rear axle is due to the connection described above of the wheel pivot 10 to the body 12b of the shock absorber 12 .

 Figures 5 and 6 show that during the upward movement of the two arms 2, 4 from their horizontal position substantially in the same

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 plane, the value of the arc of circle AA1 (seen in projection on a horizontal plane as represented in figure 6) of the displacement of the end of the arm 4 of greater length is lower than the value of the arc of circle BB2 (seen in projection on a horizontal plane as represented in FIG. 6) of the displacement of the end of the arm of shorter length 2, which results in the value of angle a greater than the value of angle P, thus corresponding the desired goal, namely obtaining the pinch angle Q of the wheel. If the arms 2,4 had remained in the same plane when moving the end of the arm 4 from point A to point Al, the arc of a circle AA1 would have been greater than the arc of a circle BB1, (always seen in projection on a horizontal plane as shown in Figure 6) which would have resulted in ru <P, going against the desired goal.

 In other embodiments, the rear axle according to the invention can be oversteer or neutral if the front bar 2 is respectively longer than the rear bar 4 or of equal length.

 The present invention naturally covers all possible variants. In particular, the shoe 18 can be housed in the central box 14, unlike what is described above. In this case, the central box 14 does not include a bottom plate 14e so that the stirrups 26 and 28 can be fixed on the bottom plate 18a of the shoe 18. The face opposite to the wheel 14f of the central box 14 may be partially full in its upper part to increase the rigidity of the pivot 10, a hollowed out space remaining in the lower part to allow the drive shaft 56 to pass. The rear transverse face 14b may be partially hollowed out to gain material.

 It is therefore understandable that the rear axle according to the invention, simple to build, is well suited to countries of low technological level, in particular for four-wheel drive vehicles.

Claims (13)

1. Rear axle of a motor vehicle comprising, for each wheel, two front transverse arms (2) and rear (4) and a longitudinal arm (6), pivotally mounted by elastic connections to the chassis (8) of the vehicle at one from their ends and to the wheel pivot (10) at their opposite ends, a shock absorber (12) which comprises a rod (12a) connected to the chassis (8) by an elastic connection and a body (12b) integral with the wheel pivot ( 10), and a suspension spring (13), characterized in that the wheel pivot (10) is in the general form of a box with welded sheet plates traversed by the lower part of the damper body (12b) rigidly fixed by box welding (10).  2. Rear axle according to claim 1, characterized in that the pivot (10) comprises a central box (14), a front box (16) to which the shock absorber body (12b) is welded and a shoe (18) on which are mounted by elastic pivot connections the transverse arms (2,4), the longitudinal arm (6) and the suspension spring (13), the front box (16) and the shoe (18) being rigidly connected by welding to central box (14).  3. rear axle according to claim 2, characterized in that the front box (16) comprises an upper plate (16a) and a lower plate (16b) connected by at least one side plate (16c), the lower part of the body d shock absorber (12b) passing through the upper plate (16a) and the lower plate (16b) along a substantially vertical axis and being welded to these upper (16a) and lower (16b) plates.  4. rear axle according to claim 2 or 3, characterized in that the shoe (18) comprises a bottom plate (18a) and at least two vertical edges before (18b) and rear (18c) substantially transverse, the <Desc / Clms Page number 12>  front (2) and rear (4) transverse arms being respectively linked by one of their elastic connections to the front (18b) and rear (18c) edges, the longitudinal arm (6) and the suspension spring (13) being linked by one of their elastic connections to the bottom plate (18a).  5. Rear axle according to claim 4, characterized in that the central box (14) comprises two front transverse side plates (14a) and rear (14b) connected by at least one lateral connection plate (14c) on the wheel side to which is fixed a wheel stub axle (20), and by a bottom plate (14e), the central box (14) being at least partially engaged in the shoe (18) and resting by its bottom plate (14e) on the bottom plate (18a) of the hoof.  6. Rear axle according to any one of claims 1 to 5, characterized in that the suspension spring (13) has the general shape of a Q, one end of the spring (13) being connected to the chassis (8) by an elastic pivot connection around a transverse axis (31), its opposite end being linked to the pivot (10) by an elastic pivot connection around another axis (30).  7. rear axle according to claim 4 or 5, characterized in that the bottom plate (18a) of the shoe (18) carries, on its underside, at least first (26) and second stirrups (28), one end of the longitudinal arm (6) coming to be articulated in the first stirrup (26), and one end of the suspension spring (13) coming to be articulated in the second stirrup (28).  8. Rear axle according to claims 5 and 6 combined, characterized in that the axes (31) and (30) of the pivot connections of the ends of the suspension spring (13) are located in the same median vertical plane of the front transverse lateral plates (14a) and rear (14b) of the central box (14). <Desc / Clms Page number 13>  9. rear axle according to claim 5, characterized in that the front box (16) is welded to an outer face of the front transverse plate (14a) of the central box (14) 10. Rear axle according to any one of claims 2 to 9, characterized in that the central box (14) has the general shape of a rectangular parallelepiped of which a side face opposite the wheel (14f) is at least partially hollowed out .  11. Rear axle according to claims 5 and 10 combined, characterized in that a drive shaft (56) passes through the central box (14) passing through a hollowed out part of the face opposite the wheel (14f), the shaft motor (56) being engaged by one end in the center of the wheel stub axle (22).  12. Rear axle according to claim 11, characterized in that the axis of the drive shaft (56) is located in the median plane of the front (14a) and rear (14b) transverse plates.  13. Rear axle according to claim 5, characterized in that a square piece (24) is rigidly connected to the central box (14) on the side opposite the wheel, in the extension of the angle between the bottom plate ( 14e) of the central box (14) and the front side plate (14a) of this box, an axis (52) of the pivot link of the front transverse arm (2) passing through both the front edge (18b) of the shoe and the angle piece (24).