EP1831037A1

EP1831037A1 - Suspended axle for a vehicle

Info

Publication number: EP1831037A1
Application number: EP05817421A
Authority: EP
Inventors: Francis Aubarede; Bruno Guimard
Original assignee: Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Current assignee: Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Priority date: 2004-12-22
Filing date: 2005-12-16
Publication date: 2007-09-12
Also published as: WO2006067087A8; FR2879508B1; CN101084127A; FR2879508A1; JP2008524069A; US20080111336A1; WO2006067087A1

Abstract

The invention relates to a suspended axle for a vehicle, comprising a longitudinal arm (5) for each wheel (2), wherein said arm is articulated in relation to the shell of the vehicle in order to enable clearance of the suspension of the wheel, wherein the axle comprises a torsion bar (10), wherein each extremity (11) of the bar is rigidly connected to a longitudinal arm in order to form a rigid part (12) of the axle and the two rigid parts of the axle are connected to each other by a torsion part (13) and the axle is provided with a wheel carrier (3) for each wheel, said wheel carrier being respectively joined to each of the rigid parts, and the axle is characterized in that each wheel carrier is joined to the respective rigid part by means of a front arm (7) and a rear part (9), wherein the links between the wheel carrier and the front arm and rear arm and the links between the front arm (20) and rear arm and the rigid parts provide pivots (14) which are substantially vertical. The axle is configured in such a way that it defines a degree of wheel lock freedom in relation to the rigid part about a lock axis (AB) which is substantially vertical and which intersects with the ground both outside and to the rear of the wheel base (BR).

Description

Suspension axle for vehicle

The present invention relates to the ground connection of motor vehicles, in particular the suspension and wheel support devices, more particularly the rear axles of passenger cars.

The term "ground connection" covers all the elements and functions present, active or influential in the relationship between the vehicle body and the ground on which it moves. The following elements are therefore part of the ground connection: tire, wheel, wheel bearing, wheel carrier, brake components, suspension elements (arms, triangles, strut, etc.), springs, shock absorbers, articulations , anti-vibration parts, anti-roll systems, anti-lock, anti-skid, steering system, trajectory control.

The suspension devices have two main functions that must be provided simultaneously at any time during operation. One of these functions is to suspend the vehicle, that is to say allow substantially vertical oscillations of each wheel depending on the load applied to this wheel. The other function of these devices is to guide the wheel, ie to control the angular position of the wheel plane.

The term "wheel plane" is the plane, connected to the wheel, which is perpendicular to the axis of the wheel and which passes through the center of the static contact area on the ground when the wheel is vertical. The wheel plane thus defined is therefore integral with the wheel axle and its orientation varies as that of the wheel.

The angular position of the wheel plane relative to the vehicle body is defined by two angles, the camber angle and the steering angle. The camber angle of a wheel is the angle separating, in a transverse plane perpendicular to the ground, the wheel plane of the median plane of the vehicle. The steering angle of a wheel is the angle separating, in a horizontal plane parallel to the ground, the plane of the wheel of the median plane of the vehicle.

The term "wheel base" is the point of intersection of the wheel plane, the ground plane and the vertical plane containing the wheel axle.

In the automotive field, a wide variety of suspension systems is proposed in particular for the suspension of the rear wheels. It is currently accepted that the so-called "multi-arm" axles make it possible to obtain good performances in terms of guidance, suspension and filtering of vibrations. However, these axles are relatively complex and use a large number of elements and points of connection to the box. Since then,

P10-1693-PCT-CL they are cumbersome, intrusive and expensive, which is why they are very little used on small or medium-sized vehicles despite the dynamic qualities that are recognized.

An object of the invention is to provide a rear axle that overcomes at least some of the aforementioned drawbacks.

This object is achieved by a suspension axle for a vehicle comprising for each wheel a longitudinal arm intended to be articulated with respect to the vehicle body to allow movement of suspension of the wheel, said axle comprising a torsion cross, each end of the cross member being rigidly connected to a longitudinal arm to form a rigid portion of the axle, the two rigid parts of the axle being interconnected by a torsion portion, said axle comprising for each wheel a wheel carrier respectively bounded at each of the rigid parts, the axle being characterized in that each wheel carrier is connected to the respective rigid part by means of a front arm and a rear arm, the links of the wheel carrier with the arms front and rear and the links of the front and rear arms with the rigid portion constituting substantially vertical pivots, the axle being configured to define a degree of freedom of steering of the wheel relative to the rigid portion about a substantially vertical axis of turning and cutting the ground outside and rear of the wheel base.

Preferably, at least one of the pivot links of the front or rear arms comprises an elastic means providing a rotation stiffness to said pivot connection. Preferably, said pivot connection is constituted by an elastomeric hinge.

According to a variant, at least one of the pivot connections of the front or rear arms comprises a flexible sheet, preferably made of steel.

Preferably, the length of the torsion portion of the cross member is greater than one third of the way of the axle.

According to a preferred embodiment of the axle, the torsion cross comprises a first tube secured to a first longitudinal arm and a transverse tube secured to a second longitudinal arm, the first tube being at least partially inserted into the second tube, the two tubes being guided in rotation relative to each other. In this case, the rear arms are preferably connected to the tubes near the junction of the cross member.

[0014] Preferably, the transverse length of the rear arm is greater than 20% of the axle track.

P10-1693-PCT-CL Preferably, the axle further comprises a suspension spring acting between the body and the wheel carrier and more preferably the axle further comprises a suspension damper also acting between the body and the ratchet.

Preferably, the axle further comprises means for actively controlling the steering movement of the wheel relative to the rigid portion.

Preferably, when the vehicle carries its reference load, the steering axis is inclined towards the rear of the vehicle by an angle of between 0 ° and 30 °, more preferably between 0 ° and 20 ° more preferably between 5 ° and 10 °.

Preferably, the front arms are oriented so as to form with the longitudinal direction of the vehicle an angle less than 60 °, more preferably less than 50 °.

The invention also relates to a motor vehicle comprising said axle.

The invention will be better understood thanks to the description of the figures which respectively represent:

Figure 1 is a schematic view from above of a first embodiment of the axle according to the invention.

Figure 2 is a schematic view from above of a second embodiment of an axle according to the invention.

Figure 3 is a schematic view from above of a third embodiment of an axle according to the invention. FIG. 4 is a diagrammatic view from above of a variant of the first embodiment shown in FIG.

Figure 5 is a perspective view of an exemplary axle according to the second embodiment of the invention.

Figure 6: top view of the example of Figure 5. - Figure 7: perspective view of a second example of an axle according to the second embodiment of the invention.

Figure 8 is a partial perspective view of a third example of an axle according to the second embodiment of the invention.

In the various figures, identical or similar elements bear the same reference numbers. Their description is therefore not systematically repeated.

P10-1693-PCT-CL In Figure 1, there is shown schematically in plan view a first embodiment of a rear axle according to the invention. The ground is parallel to the plane of the drawing and the front of the vehicle is at the top of the figure. The axle being substantially symmetrical, its description is based mainly on the left part of it.

The axle comprises for each wheel a longitudinal arm 5 intended to be articulated with respect to the vehicle body (not shown) via a hinge axis AS to allow the travel of suspension of the wheel 2. A torsion beam 10 connects the two longitudinal arms 5 and 5 '. Each end 11, 11 'of the cross member is rigidly connected to the corresponding longitudinal arm (the term "recessed" is also used). The assembly comprising the longitudinal arm 5 and the rigid end 11 of the cross member constitutes a rigid portion 12. This rigid portion is connected to the other rigid portion 12 'of the axle by means of a torsion portion 13 the crossbar to allow a different travel of the two wheels of the axle. The crosspiece participates predominantly in guiding the wheel planes, particularly with regard to the camber. In addition, the crossbar brings to the axle anti-roll stiffness mainly due to the torsional stiffness of its torsional part. An important feature of the transom is also its twist length "Lt".

The wheel axle AR is connected to the ratchet 3. The wheel carrier is hinged relative to the rigid portion 12 by means of a front arm 7 and a rear arm 9. The links constitute pivots 14 substantially vertical. The front arms 7 and rear 9 and their connections are configured to allow a degree of freedom of steering wheel-carrier 3 (and therefore the wheel 2) relative to the rigid portion 12 about an axis of rotation AB substantially vertical, located outside the wheel plane PR and behind the wheel axis AR. In this view from above, the wheel base BR appears at the intersection of the median plane PR of the wheel and the wheel axle AR. The intersection of the AB steering axis with the ground is at a distance "dx" behind the wheel base and at a distance "dy" outside the wheel base. For a compact passenger vehicle, distances dx and dy of the order of 100 mm give satisfactory results.

The pivots 14 can be made in different ways, for example using plain bearings, ball bearings, roller or needle or elastomeric joints. The pivots can also be based on the bending of a flat profile as will be seen later. Depending on the rotational angles and the expected loads, one can choose to use the technique best suited for each connection.

P10-1693-PCT-CL Generally called "axle track" the distance (V) separating the two wheel planes at ground level. In a manner known per se, in order to guarantee satisfactory durability for a reasonable weight, the torsion length Lt for this type of torsion beam is preferably greater than one third of the way of the axle, or even half.

This principle shows a principle of the invention according to which on the one hand the suspension travel of each wheel is given by the oscillation of the corresponding longitudinal arm and on the other hand the relative movements of the front arms and rear allow substantially steering movements of the wheel relative to the corresponding longitudinal arm.

To adapt the steering movements to the forces exerted by the ground on the wheel, the axle may comprise an elastic means providing a stiffness opposing the steering movement. The axle according to the invention can thus operate in a purely passive manner as a function, for example, of braking forces and transverse forces during a turn. The resilient means may be integrated with the pivot links or only some of them. For purely passive operation, pivot stiffness of the order of 100 Nm per degree may be necessary to obtain a satisfactory behavior. Naturally, this elastic return of steering by the pivots can be exerted (equally or not) by all the pivots of the axle or by a limited number of them.

The axle may also comprise active steering control means. This possibility is shown diagrammatically in the figure in the form of a cylinder 15. The active steering control means can in practice take any form allowing their control in terms of vehicle running parameters. In the case of active control, the elastic return of the steering by elastic means can be reduced or eliminated. Similarly, the distances dy and dx can be reduced compared to an axle whose operation is purely passive.

The active control means can be controlled according to various vehicle running parameters (eg speed, longitudinal or transverse acceleration, braking force, steering wheel position, speed of rotation of the steering wheel, torque exerted on the steering wheel , roll, roll speed, roll acceleration, yaw, yaw rate, yaw acceleration, wheel forces including vertical load, type of ride or desired behavior by the driver).

P10-1693-PCT-CL The cylinder 15 may also be a simple telescopic damper, ie a means of passive control of the "natural" steering movements of each wheel carrier.

In Figure 2, there is shown an advantageous embodiment of the invention wherein the torsion cross member 10 uses the principles described in EP 0904211, EP 1265763 or international application WO02 / 2238497. This type of sleeper uses mainly two coaxial tubes. A first tube (the left tube in this example) comprises a portion 18 whose section is reduced relative to that of the second tube to allow to introduce this reduced portion of the first tube into the second tube (the right tube in this example ). The two tubes can for example be guided relative to each other by elastic sleeves 20 and 22. The torsional deformations of the crossbar caused by the rolling of the body are absorbed by the elastic connection between the two tubes. . The torsional part of the crossbar is here located inside the rigid part (here the rigid part of the right side 12 '). Therefore, in the context of the present invention, the rigid portions 12 and 12 'can extend substantially to the junction 24 of the two half-cross members 16 and 16'. In this embodiment, it is then possible (and this may be particularly advantageous) to give a great length (lar) to the rear arms 9 and 9 'by articulating them on the half-rails near the junction. A consequence of this greater length of the rear arms may be a greater stability of the position of the AB steering axis.

Figure 3 shows another embodiment of the invention in which the cross member 10 uses the principles described in patent application FR 2840561. This type of cross member uses two coaxial tubes 16 and 16 '. At the junction 24 of the tubes, the tension of a bar 28 maintains a ball bearing 26 under pressure to ensure the coaxial guidance of the half-cross members 16 and 16 '. The bar 28 also works in torsion so as to offer resistance to the relative rotations of the tubes, that is to say to the torsion of the crosspiece 10. The rigid parts 12 and 12 'therefore extend here as far as the joint of the two half-sleepers since the torsion portion of the crossbar is placed inside the tubes.

Figure 4 schematically shows a particular embodiment of the invention combining a torsion cross member 10 similar to that of Figure 1 and rear arm lengths (lar) comparable to those of Figures 2 and 3. To do this the rigid parts 12 and 12 'are extended by offset parts 30 and 30'. Thus, the length of the rear arms 9 and 9 'is no longer limited by the reduced transverse length of the rigid parts, the rigid parts of reduced length being typical of a single-piece torsion beam.

P10-1693-PCT-CL Figures 5 to 9 show embodiments of axles according to the invention. These examples are based on the use of a torsion crossbar with two coaxial tubes and guided in rotation in one another as described above in Figure 2. Of course, as we have just seen, other types Twisted sleepers can be used.

The axle of Figures 5 and 6 uses front and rear arms made of sheet steel for example stamped. The pivot 141 of the front arm 7 on the longitudinal arm 5 is formed by the bending of a limited area of the sheet. The front arm is connected to the wheel carrier 3 by a pair of elastomeric hinges arranged so as to define a pivot axis 142. Likewise, the pivot 144 of the rear arm 9 on the half-cross member 16 is formed by the flexion d a limited area of the arm plate. The connection of the rear arm to the ratchet uses a pair of elastomeric hinges arranged to define a pivot axis 143.

Ribs are stamped into the plate of the arms 7 and 9 so as to provide the necessary rigidity to the arms outside the areas intended to flex. It is understood that the flexible zones make it possible to achieve the necessary pivot but also to integrate the elastic means adapted to oppose a stiffness to the steering movement and therefore useful for control as described above. Elastomeric joints can also bring such stiffness.

The example of Figure 7 is similar to that of Figures 5 and 6. However, this axle differs from the previous one in that all the pivots of the front and rear arms are made by bending the sheet metal arms. The rigidity of the arms is reinforced by the use of a profile comprising, in addition to the stamped ribs, raised lateral portions 34. The ratchet 3 here comprises a support 36 intended to receive the end of a helical spring of suspension

(not shown) The rear arm 9 is shaped to allow the passage and movements of such a spring. The support 36 may also receive the lower eye of a telescopic suspension damper.

Naturally, the suspension spring may be of any other type, for example pneumatic, elastomeric or flexible blade.

The various elements of this variant (crossbar, arm, wheel carrier) can all be assembled by welding. An interest of such an axle is of course a number of parts and a reduced industrial cost.

P10-1693-PCT-CL Figure 8 shows an axle similar to that of Figure 7 with the difference that the front arm 38 here has a tabular profile and is articulated at both ends by means of elastomeric bearings.

The various figures show joints with horizontal axes of the longitudinal arm relative to the body. Other orientations are of course applicable, articulations with vertical axes can in particular facilitate the industrial assembly of the axle on the body. In addition, the axis of these joints is shown inclined relative to the transverse direction of the vehicle as is known per se for the purpose of creating a steering effect of the longitudinal arms. However, the invention allows the steering of the wheels independently of the steering of the longitudinal arms, a steering effect of the longitudinal arms is not necessarily necessary and non-inclined joints can be preferred in terms of comfort. Preferably, the axis of the cross member (AT in the figures) is offset towards the rear of the axle relative to the joints of the longitudinal arms to the body as shown but this is not essential to the invention .

The invention allows the realization of axles little complex and whose elastocinematic performance is quite interesting. For example, it has been possible to obtain, according to the invention, a plier variation under longitudinal force (braking) greater than 0.05 degree per kiloNewton (° / kN), a transverse force plier variation greater than 0.1 ° / kN and a variation camber under transverse load less than 0.5 ° / kN.

According to the invention, the steering axis AB is substantially vertical. In practice, its orientation varies with the travel of suspension, that is to say with the oscillations of the longitudinal arms of the axle. When the vehicle carries its reference load, that is to say when it is in running order (full tank) and carries 2 passengers sitting in the front seats, the steering axis AB is preferably inclined towards the rear of the vehicle. vehicle, for example at an angle between 0 ° and 30 °, more preferably between 0 ° and 20 °, more preferably between 5 ° and 10 °. In this way, the transverse forces can also cause interesting camber variations. When it is said that the axis is inclined towards the rear, this means for example that for a left wheel seen from the outside of the vehicle, the axis AB is inclined by the indicated angle in the clockwise direction relative to vertically.

According to another preferred feature of the invention, the front arms (reference

7 and T in the figures) are oriented so as to form an angle α less than 60 °, more preferably less than 50 ° with the longitudinal direction of the vehicle. This

P10-1693-PCT-CL The preferred characteristic is shown in FIG. 2, but it obviously concerns all the embodiments of the invention.

P10-1693-PCT-CL

Claims

claims

A suspension axle for a vehicle comprising for each wheel (2) a longitudinal arm (5) intended to be articulated with respect to the vehicle body in order to allow movement of suspension of the wheel, said axle comprising a torsion beam (10) each end

(11) of the cross member being rigidly connected to a longitudinal arm to form a rigid portion

(12) of the axle, the two rigid parts of the axle being interconnected by a torsion portion (13), said axle comprising for each wheel a wheel carrier (3) respectively connected to each of the rigid parts, l axle being characterized in that each wheel carrier is connected to the respective rigid part by means of a front arm (7) and a rear arm (9), the links of the wheel carrier with the front arms and rear and the links of the front and rear arms with the rigid portion constituting pivots (14) substantially vertical, the axle being configured to define a degree of freedom of steering of the wheel relative to the rigid portion around a substantially vertical steering axis (AB) and cutting the ground outside and behind the wheel base (BR).

2. Axle according to claim 1 wherein at least one of the pivot links of the front or rear arms comprises an elastic means providing a rotational stiffness to said pivot connection.

3. Axle according to claim 2 wherein said pivot connection is constituted by an elastomeric hinge.

4. Axle according to claim 2 or 3 wherein at least one of the pivot links (141) of the front or rear arms comprises a flexible sheet, preferably steel.

5. Axle according to one of the preceding claims wherein the length of the torsion portion (Lt) of the crossbar is greater than one third of the track (V) of the axle.

6. Axle according to one of claims 1 to 4 wherein the torsion cross comprises a first tube integral with a first longitudinal arm and a second tube integral with a second longitudinal arm, the first tube being at least partially inserted into the second tube, the two tubes being guided in rotation relative to each other.

P10-1693-PCT-CL

7. Axle according to claim 6 wherein the rear arms are connected to the tubes, near the junction (24) of the cross.

8. Axle according to one of the preceding claims wherein the transverse length of the rear arm (lar) is greater than 20% of the way of the axle.

9. Axle according to one of the preceding claims further comprising a suspension spring acting between the body and the wheel carrier.

10. Axle according to one of the preceding claims further comprising a suspension damper acting between the body and the wheel carrier.

11. Axle according to one of the preceding claims further comprising active control means (15) of the steering movement of the wheel relative to the rigid portion.

An axle according to one of the preceding claims wherein, when the vehicle is carrying its reference load, the steering axis (AB) is inclined towards the rear of the vehicle by an angle of between 0 ° and 30 °, preferably between 0 ° and 20 °, more preferably between 5 ° and 10 °.

13. Axle according to one of the preceding claims wherein the front arms (J, T) are oriented so as to form with the longitudinal direction of the vehicle an angle (α) less than 60 °, preferably less than 50 °.

P10-1693-PCT-CL