FR2522590A1 - Suspension system for vehicle - uses trapezoidal linkage to attach each wheel to vehicle bodywork to allow simultaneous tilting - Google Patents

Abstract

The suspension for a vehicle comprises at least one pair of wheels (4) arranged symmetrically about the longitudinal plane (Q) of the vehicle. An axle (1) is pivotally attached to the vehicle about its centre and carries bars (2) at its ends which support the wheels. At rest on a level surface, each bar forms one side of a trapezium, the major base of which consists of half the axle (1). The minor base is defined by a line joining the free ends of the bars whilst the side opposite the bar is formed by the longitudinal plane of the vehicle.

Description

 The present invention relates to a suspension system for a vehicle resting on a support surface by means of tilting support members such as wheels.

 The invention also relates to a vehicle provided with such a suspension system.

 Although, in what follows, the invention is mainly described with reference to land vehicles provided with wheels, it also relates to the case where the support members are pads or floats.

 The suspension system referred to here comprises at least one pair of symmetrical support members, in the rest position, with respect to the longitudinal plane of symmetry of the vehicle. It applies equally to tricycles or quadricycles as to two-wheeled vehicles of the trailer type.

 I1 comprises a main carrier axle articulated in its middle on the vehicle and two lateral bars articulated at the ends of this axle, directed transversely to the support surface, and to which the support members are fixed directly or indirectly.

 Known systems of this kind essentially have the aim of allowing the inclination of the wheels relative to the vertical, in particular when cornering in order to resist centrifugal thrust and skidding while benefiting from a wider contact surface of the tires with the ground, and therefore better grip. In most of these systems, the wheels are fixed on parallel vertical bars articulated at the end of the axle, and the inclination of the wheels results from a deformation of the structure in parallelogram, these bars being connected together by a second axle the same length as the first. In the other cases, these parallel vertical bars rest on longitudinal arms carrying the wheels.

 Such systems are essentially unstable. On flat ground at rest, any initiated inclination tends to increase; the same is true on sloping land.

 On light vehicles, a mode of driving similar to that of bicycles is used during the evolutions, to ensure stability by slight actions on the steering. On heavy vehicles, servo devices are used, in particular tilt control cylinders, which can also be controlled automatically by devices sensitive to movement such as pendulums, gyroscopes, electrical sensors, etc.

 In both cases, either stability is poorly ensured, or it is only obtained by means of complicated and expensive devices with deferred action, making rapid changes perilous.

 The present invention aims to provide a suspension system which tends by itself to adopt a stable position, whatever the nature of the terrain, including during rapid or tight evolutions.

 This object is achieved, in accordance with the invention, by the fact that, the vehicle being at rest on a horizontal bearing surface, each side bar constitutes one side of a trapezium, the base of which is formed by one half of the main axle and the other base of which is carried by a line joining the ends of the side bars which are not articulated to the ends of the main axle, the side of the trapezoid opposite the side bar being secured to the vehicle.

 This geometry highlights a point which will be referred to hereinafter as the tilt point11, and which constitutes a center of moment with respect to which the weight of the vehicle exerts a restoring torque, that the support members are inclined with respect to a horizontal support surface or that these members are vertical with respect to a support surface in lateral cant.

 It will be noted that, in what follows, the word "vehicle" designates only the suspended part, to the exclusion of the suspension to which it is fixed.

 According to a first embodiment of the invention, each end of the side bars not connected to the main axle is connected to the vehicle by an auxiliary axle bar articulated on the vehicle.

 With this type of suspension, which will be, in what follows called "oscillating axles", the geometrical location of the cant point, when the support members tilt relative to the ground, is a concave curve upwards, so that the greater the inclination, the greater the restoring force. Stability therefore increases with tilt.

 As a variant, the vehicle comprises an intermediate piece rigidly fixed on it, at the ends of which the bars forming the auxiliary axle are articulated.

 According to a second embodiment, the ends of the lateral bars not connected to the main axle are respectively connected to longitudinal bars themselves articulated on a common axis transverse to the longitudinal plane of symmetry of the vehicle.

 With this second type of suspension, which will hereinafter be called a pendulum ", the geometrical location of the cant point when the axle (or pendulum) is in the upper position relative to the side bars is a downward concave curve, so that, in this variant (balance in high position), the more the inclination increases and the more the cant point moves away from the structure, reducing the restoring force.

 The choice between the two embodiments in their respective variants will depend on the expected operating conditions of the vehicle.

 In the type of pendulum suspension, the support members are preferably fixed to the longitudinal bars, and not directly to the side bars, which gives a certain ease of adaptation.

 In these two embodiments, the main axle can be located above or below the side bars which thus work, respectively in compression or in traction.

 According to a preferred embodiment of the invention, the system comprises means for modifying the orientation of the support members around an axis substantially perpendicular to the trajectory of the support member on the support surface as a function of the inclination of these members relative to the bearing surface.

 When cornering, the inclination of the vehicle thus causes a lateral drift whose effect is added to that of the directional wheels.

 Other features and advantages will emerge from the detailed description which follows.

In the appended drawings, given by way of nonlimiting examples:
. Figure 1 is a schematic perspective view of the embodiment with oscillating axles, in a variant with upper main axle;
Figure 2 is a view similar to Figure 1, in a variant with lower main axle;
. Figure 3 is a schematic view from the rear, applying to the two previous variants;
Figures 4 to 5 are views similar to Figures 1 to 3 but in the pendulum embodiment;
Figures 6 and 7 are schematic views from the rear, applying to the variants of Figures 4 and 5;
Figures 8 and 9 show the behavior
Static of the system in lateral slope, respectively in the two embodiments ;;
FIGS. 10 and 11 show the dynamic behavior of the system when cornering on a horizontal track, with insufficient speed, in the two embodiments;
Figures 12 and 13 show this same behavior when the speed is optimal;
Figures 14 and 15 show this same behavior when the speed is excessive;
Figures 16 and 17 show, schematically, practical embodiments of the oscillating axle system;
. Figure 18 is a diagram relating to the embodiment of Figure 17;
. Figure 19 is a schematic view of a particular elastic suspension device;
. Figure 20 is a schematic view of a first drift device;
. FIG. 21 is a schematic view of a second drift device;
. Figure 22 is a schematic view of another particular elastic suspension device;
Figures 23 to 32 are examples of three-cycle vehicles equipped with a suspension system according to the invention;
Figures 33 and 34 are examples of quadricycle vehicles equipped with a suspension system according to the invention;
. Figure 35 is an example of a skid vehicle fitted with a suspension system according to the invention;
. Figure 36 is an example of a vehicle with a pair of wheels equipped with a suspension system according to the invention;
Figures 37 and 38 are examples of sail vehicles equipped with a suspension system according to the invention.

 Referring to Figure 1, the suspension system shown at rest in its embodiment with oscillating axles, comprises an upper main axle 1 articulated in the middle on a vehicle not shown. Two side bars 2 are articulated at the ends of the axle 1 and directed towards the ground. To these bars are attached rockets 3 carrying wheels 4. The bars 2 are arranged obliquely so that their extensions intersect at a point A located below the surface of the ground. In what follows, point A will be called superelevation point. In the rest position of the vehicle, shown in the figure, the assembly described is symmetrical with respect to the plane Q of longitudinal symmetry of the vehicle.

 The ends of the bars 2 not connected to the axle 1 are connected together by a bar forming an auxiliary axle and consisting of two equal half-bars 5a, 5b articulated at 6 at their junction.

The articulation 6 is subjected, by known mechanical means, to remain in the plane Q whatever the deformations undergone by the bar system.

 The vehicle also comprises other ground support members (not shown), such as a third steering wheel forming a tricycle, or a second pair of wheels linked to a suspension system such as that which has just been described. Whether this system is single or double, the articulation of the axle 1 on the vehicle allows it to oscillate around a horizontal axis 7 located in the plane Q.

 Auxiliary bars 8 connect the ends of the axles to points 9, 10 located in the plane Q to maintain the oscillations of the axles in a plane perpendicular to the axis 7, the connection to point 10 being an articulation.

 It is understood that the expressions "horizontal" and "vertical" must be understood, unless otherwise indicated, as referring to a vehicle at rest on horizontal ground.

 FIG. 2 shows a variant of the embodiment with oscillating axles in which the main carrying axle is in the low position and the auxiliary axle Sa, 5b in the high position. The fixed link 9 and the articulation 10 are then inverted. The same reference numbers have been kept in this figure as in Figure 1 to designate the elements exercising the same function.

 In the variant of FIG. 2, the static and dynamic behavior of the system, which will be described later, is substantially the same as in the case of FIG. 1.

 Figure 3 is a rear view of the embodiment of Figure 1, but it would apply equally to that of Figure 2 by reversing the axles. I1 results from the description which has just been made that the quadrilateral ABCD is a trapezium of which a base AB is constituted by one half of the main axle 1, of which another base CD is carried by a line joining the ends of the bars 2 not articulated at the ends of the main axle 1, one lateral side AD of which is constituted by a bar 2 and the side BC of which opposite this bar forms part of the vehicle as defined above.

 We will now describe, with reference to FIG. 4, the suspension system in its pendulum embodiment in the variant where the axle is in the high position.

 This system comprises a main axle 11 (called a pendulum) articulated in its middle to the vehicle (not shown) in the plane Q of longitudinal symmetry of the latter. Side bars 12 are articulated at the ends of the axle 11 and directed obliquely so that their extensions intersect at a point of overhang ss located below the ground.

 At their lower end, opposite the articulation with the axle 11, the bars 12 are fixed to longitudinal bars 15 which extend by converging towards the plane Q up to an axis 16 transverse to the vehicle on which they are articulated by bearings 15a.

 In contrast, the bars 15 end in bent portions 15b at the end of which are fixed rockets 13 carrying wheels 14.

 The articulation of the axle 11 on the vehicle allows it to oscillate around a horizontal axis 17 situated in the plane Q, auxiliary bars 18 joining the ends of the axle to a point 19 of the axis 17 for force the axle to remain perpendicular to this axis.

 In this embodiment, the role of the auxiliary axle of the embodiment with oscillating axles is, to a certain extent, held by the longitudinal bars 15.

 There is shown in FIG. 5 a variant of the pendulum embodiment in which the main axle 11 is in the low position relative to the side bars 12. Again, the same reference numbers have been kept as in FIG. 4, for facilitate understanding.

 The static and dynamic behavior of this variant differs from that of the variant with the axle in the high position, and is rather similar to that of the version with oscillating axles.

 In rear view, Figures 6 and 7 apply respectively to Figures 4 and 5. In the plane of Figures 6 and 7, the bars 15 are seen in projection. These trapezoids ABCD of FIG. 3 are immediately found in these figures.

 We will now describe, with reference to FIG. 8, the behavior of the suspension system of the oscillating axle type on a ground S in lateral gradient.

 The weight P is exerted on the wheels 4a, 4b and applied to the center of gravity G of the system, as well as the reactions R exerted by the ground on the wheels.

 The deformation of the polygon of the bars causes a certain pinching of the wheels, the planes of which converge towards the ground. To simplify the drawing, it has been admitted, which is moreover substantially exact in practice, that the upstream wheel 4b remains vertical, and that the downstream wheel 4a inclines downstream from the slope.

 The components of the weight P have been represented according to the side bars 2, which converge at the point of superelevation a, the location of which is a curve r when the inclination of the ground varies. The components of the reactions R have also been represented in the directions perpendicular to the bars 2, which converge at a point of counter-slope 8 ′. These forces tend to compress the structure, thus giving it the equivalent of a certain elasticity and their arrangement with respect to the P and R forces shows that they would tend to bring it back to its rest configuration if the ground became horizontal again.

 Indeed, the reaction R on the downstream wheel 4a, not being in the plane of the wheel, generates a reversal torque as a function of the inclination of the structure which has been represented by a force r1 applied at the corresponding end of axle 1.

This force has been brought back to r'l at the center of gravity G.

 On the other hand, the weight P has been broken down along GA and in the perpendicular direction, which shows a force r producing a restoring torque, also a function of the inclination of the structure. There will therefore be an inclination of the structure for which the overturning torque and the restoring torque will be exactly opposed to give a stable inclination of the structure.

 At rest on horizontal ground, the vehicle being vertical, these torques are zero and the structure is only subjected to its internal stress forces generated by the weight and which keep it stable by compressing it.

 Due to the concavity of the curve, the steeper the slope and the more the vehicle inclines relative to it, the more the tilt point A approaches the center of gravity G, which has the effect of increasing further the stability of the structure.

 If it were admitted that the upstream wheel 4b was also inclined, this would result in an additional force r2 which would be added to the force r1 and the reasoning would not be modified thereby.

 We will now describe, with reference to FIG. 9, the behavior of the balance system in the axle variant in the high position on a ground S in lateral gradient.

 In this embodiment, because the longitudinal bars 15 carrying the wheels are articulated on the axis 16 perpendicular to the plane of symmetry Q of the vehicle, the planes of the wheels remain parallel and inclined at the same angle on the vertical. Under these conditions, each of the wheels is the seat of a reversal torque materialized, respectively, by forces rl and r2, that is to say by a resultant r 'whose moment relative to the point of superelevation A is balanced by the moment of the component r of the point P in the direction perpendicular to GA, this moment being that of a restoring torque.

 An important difference of this variant with the type with oscillating axles is that here the curve P is convex upwards, so that, when the inclination increases, the cant point A moves away from the center of gravity G and the forward slashes 12 tend to become parallel. If this limit is reached, the structure becomes unstable and collapses.

 The balance system in the axle variant in the high position is therefore of application limited to relatively uneven terrain, where the lateral slopes are small.

 It is evident, in FIGS. 8 and 9, that, if for some reason, the line of action GP of the weight P passed to the right of the line Q representing the median plane of the vehicle, the structure would collapse towards the up the slope. The condition of self-stability is therefore that the center of gravity G projects vertically onto the segment AH of the curve p, between point A and point H where this curve intersects the line Q.

 We will now describe, with reference to FIG. 10, the dynamic behavior, in turns, of the oscillating axle system, on the assumption that the speed of the vehicle, at the instant considered, is too low to ensure stability.

 The force F applied to the center of gravity G is the result of the weight P and the centrifugal force f.

In FIG. 10, we have placed ourselves for clarity in the particular case where the force F is located in the median plane of the vehicle. The reactions Ra and Rb of the horizontal ground S are oblique and take account of the friction reactions, which are different for the two wheels, since these wheels have trajectories with different radii of curvature.

The reactions Ra and Rb generate torques applied to the wheels represented by forces r1 and r2
These forces r1 and r2 are here, when F is in the plane
Q of symmetry of the vehicle, practically equal but in opposite directions, so that their resultant applicable to the center of gravity G (referenced r 'in the following figures) is negligible, which results in the practical absence of a righting torque for the deformable structure around its cant point A.

 The deformable system of the suspension, only subjected at the time of the component r of the force F in the direction perpendicular to GA generating a tilt torque around the cant point A, will therefore tend to be deformed further and to tilt the vehicle, but, by the driving effect of the steered wheels (not shown), this will result in a reduction in the radius of curvature of the trajectory which will have the effect of increasing the centrifugal force by increasing the angular speed and a new inclination stable will be found, when r 'ceasing to be zero will equal r, the opposite couples of straightening and tilting then becoming equal.

 In FIG. 11, the same driving circumstances have been represented in the case of a pendulum suspension system 11 when the latter is in the high position. It will be recalled that in the pendulum form the wheels 14a and 14b remain parallel to the median plane Q of the vehicle.

 In the case of FIGS. 12 and 13, it is assumed that the speed of the vehicle is optimal, so that the resultant F of the forces applied to the vehicle intersects the curve P on the segment AH. Under these conditions, there is, without modification of the radius of curvature, a precise inclination for which the righting torque balances the tilting torque.

 We note that, the closer the superelevation point A is to the center of gravity G and the weaker the torques around A for applied forces in G, which is to say that the closer A is to G, the more the oscillation range of the structure around its equilibrium position is large.

 The range of self-stability can be widened by the presence of steered wheels having a driving effect, which, in the event of turning, modifies the relative positions of the points of application of the reaction forces of the ground.

 This hunting effect can possibly create an additional torque of tilt or straightening depending on whether the point of contact with the ground of a steering wheel 4c (FIG. 12) in the case of a tricycle, or of a central steering wheel. equivalent fictitious in the case of a quadricycle, is respectively on the left (on the figure) or on the right of the plane Q1 projecting the force F.

 In the case of FIGS. 14 and 15, it is assumed that the speed of the vehicle is too high to allow a stable inclination. For greater clarity, the particular case is shown where the resultant F of the forces applied to the center of gravity G passes through the superelevation point A, which cancels the tilt torque, referenced r in the previous figures. The only action therefore is the righting torque resulting from the force r 'applied in G, which tends to bring the vehicle back to the vertical position and, by the driving effect of the steering wheels, to bring its trajectory closer to the straight line.

At constant linear speed, an equilibrium position will be found, where the tilt torque will have ceased to be zero and where the righting torque will have decreased.

 In the case of the oscillating axle system, the straightening is further helped by the pinching of the wheels. Indeed, any rolling assembly tends to occupy the widest possible support polygon, which here corresponds to a zero pinch, that is to say in the vertical position on a horizontal ground.

 We will now describe, with reference to Figures 16 and 17, a practical embodiment of the oscillating axle system.

 The main axle 1 being in the low position (FIG. 16), the bars 5a and 5b forming the auxiliary axle each articulate at one end of an intermediate piece 50 rigidly fixed to the vehicle. The lengths of the bars 5a, 5b and of the part 50 are such that in the rest position the length of the auxiliary axle is equal to that of the main axle. In other words, in the case of FIG. 16, the sum of the lengths of the bars 5a and 5b, reduced by the length of the part 50, is equal to the length of the main axle 1. It follows that at rest the side bars 2 are parallel and vertical. In any other configuration, the auxiliary axle, by the partial or total development of the elements which compose it, is longer than the main axle.

 If - is the angle formed by a straight line passing through the middle of the main axle 1 and one end of the intermediate piece 50 with the plane of symmetry Q of the vehicle, the cant point A is obtained by leading through the ends of the main axle of the lines making the angle with the side bars 2, towards the outside of the vehicle.

 When the main axle is in the high position (Figure 17), the construction is similar, but the sum of the lengths of the bars 5a, 5b, and the piece 50 is equal to the length of the main axle, so that at rest, these elements being fully deployed and aligned, the two axles are of equal length and the side bars 2 are parallel and vertical. In any other configuration, the secondary axle is shorter than the main axle, due to the partial folding of the elements that compose it.

 The superelevation point A is obtained as above, but this time carrying inwards the lines forming the angle Oc with the side bars 2.

 In FIG. 18, where the rest position of the device in FIG. 17 is shown diagrammatically, we find the trapezoid ABCD mentioned above, with the side AD formed by a side bar 2, a base AB formed by one half of the axle main 1, a CD base carried by the right joining the ends of the bars 2 not linked to the main axle, and a side BC secured to the vehicle.

 We would find a trapezoid of the same kind in the case of Figure 16.

 Referring to Figure 19, the axis 3 of the wheel 4 is secured to the side bar 2 by means of a telescopic device 21 with springs, which has the effect that, when the vehicle is tilted, each wheel moves in its plane (according to the arrows), the body of the vehicle moving parallel to its plane of symmetry Q. The advantage is that it does not cause lateral offsets of the suspended mass when the vehicle is moving on a slope in lateral slope .

 In another type of embodiment (FIG. 20), the main axle 1 is made flexible by being produced in the form of a leaf spring. The wheels are then forced to move parallel to themselves and perpendicular to the bearing surface, according to the arrows. The body of the vehicle, when tilted relative to the bearing surface, also moves perpendicular to the bearing surface. This arrangement has the advantage of not causing lateral offsets when the vehicle is moving in a curve on horizontal ground.

 In this embodiment, the spindles 3 of the wheels are fixed on spindle carriers 22 pivotally mounted on the side bars 2, the rotation of which is controlled by rods 23 articulated at symmetrical points of the auxiliary axle 5a, 5b. When the vehicle tilts, the wheels pivot slightly around an axis X located in their plane and perpendicular to the path T of the wheels on the ground. It results from this steering induced a drift movement of the vehicle which has in particular the effect of reducing the tendency to skid at the entry of turns and in the changes on the slope.

 On the other hand, the yaw axis is moved towards the center of the vehicle's support polygon, which has the effect of improving the maneuverability, since the trajectories of the front and rear wheels tend to merge.

 In the embodiment of Figure 20, the rods 23 could as well be articulated on the main axle or at points in the body of the vehicle.

 In another embodiment (Figure 21), the side bars 2 are provided with yokes 24 which pivot nuts 28 which themselves are articulated on the auxiliary axle 5a, 5b. The axes of the nuts 28 are not parallel but converge towards a point K, called center of drift located in a plane R perpendicular to the axle 5a, 5b in its middle, at a level higher than this axle relative to the ground, and towards the end of the vehicle opposite to that where the pair of wheels in question is located.

In order to allow the orientation movement of the wheels, the bars 2 are connected to the axle 1 by ball joints 26.

 In another embodiment (FIG. 22), the main axle 1 carries, at its ends, yokes 27 where the nuts 28 pivot whose axes converge towards the point K defined above, and in which the arms 29 are articulated wheel carriers integral with the side bars 2. The nuts 28 also carry levers 31 which compress springs 32 bearing on the axle 1, thus achieving another mode of elastic suspension.

 Figures 23 and 24 show motor tricycles, of the motorcycle type.

The rear suspensions are of the swing axle type, with main axle 1 in the low position (figure 23) or in the high position (figure 24). The elastic suspension is of the telescopic device type 21.

 In the tricycle of FIG. 24, the bars 5a and 5b forming the auxiliary axle are articulated on a central part 50 secured to the vehicle forming an intermediate part, according to the principle described above.

The suspension of the tricycle in FIG. 25 is of the pendulum type. The balance 11 is in the high position, above the side bars 12 which are articulated on the longitudinal bars 15 articulated at their other end by the bearings 15a carried by the axis 16 perpendicular to the vehicle. The wheels are fixed on the bent parts
15b extending the longitudinal bars 15.

 The tricycles of FIGS. 23 to 25 do not include any device for drift by induced steering.

 With reference to FIG. 26, another type of tricycle vehicle comprising a main axle made in three parts 1a, 1b, 1c in order to make it flexible.

The lateral parts 1a and 1b have levers 33 which
compress springs 34 bearing on the central part lc.

 Springs 35 secure the central part lc with the lower axle in two parts Sa, 5b and force the two axles to move in parallel while ensuring part of the elastic suspension function.

 Rods 23 articulated on the central part lc of the main axle and on the pivoting knuckles 22 make it possible to obtain the drift by induced deflection when the vehicle tilts.

 The tricycle vehicle shown in FIG. 27 is of the same kind as the previous one and, in contrast, has an auxiliary axle in three parts Sa, 5b, 5c.

However, the lateral parts Sa, 5b consist of struts articulated around the transverse axis of the central part 1c which contains a torsion bar exerting an anti-roll effect. The elastic suspension is provided by springs 35 taking effect on the main axle 1a, 1b and the central part 5c of the auxiliary axle.

 The lateral bars 2, the outline of which is shown along the dashed lines 2a, are articulated on the upper axle by Cardan joints 36, and on the lower axle by omnidirectional ball joints 37.

 With reference to FIG. 28, a tricycle vehicle of the oscillating axle type, comprises a rigid main axle 1 connected by struts 38 to torsion bars contained in a carrying axle 101 fixed to the vehicle in the middle. The auxiliary axle comprises two parts 5a, 5b articulated around an axis 39 contained in the longitudinal plane of symmetry of the vehicle.

 The side bars 2 are U-shaped and are shown diagrammatically by their sketch line 2a. They include a yoke 24 in which a nut 28 rotates. The nuts 28 are connected together by a torsion bar which exerts a restoring torque and causes an anti-roll effect.

 The axes of the nuts 28 converge towards a point K situated in the plane of symmetry of the vehicle, towards the front and above the plane of the rear suspension with respect to the ground. The lateral bars are articulated on the auxiliary axle Sa, 5b by omnidirectional ball joints 37.

 I1 results therefrom, under the effect of an inclination of the vehicle, an induced steering causing an effect of drift.

 The tricycle vehicle shown in FIG. 29 is also of the oscillating axle type, with a one-piece auxiliary axle 5 articulated in its middle around an axis 42 located in the plane of symmetry of the vehicle, and a lower main axle 1a, 1b in two parts articulated on a common axis 43 also contained in the plane of symmetry.

 The auxiliary 5 and main axles 1a, 1b are articulated at their ends to lateral oblique bars 2 which join them together, and of which the lines of drawing have been shown in 2a.

 The steering knuckles 3 of the wheels 4 are not directly connected to the bars 2, but by means of a share of upper struts 44 connected together by an internal torsion bar to the auxiliary axle 5 in one piece and playing an anti-roll role, and on the other hand of lower struts 45 integral with the main semi-axles 1a, 1b which provide elastic suspension thanks to the torsion bars which they contain.

 The connection between the stub axle 3 and the struts 45 is effected by means of a yoke 24 secured to the stub axle and a pivoting nut 28 secured to the strut. The axes of rotation of the nuts 28 converge towards a point K defined as in the previous example. The induced steering effect is obtained by virtue of the fact that the connection of the stub axle 3 with the strut 4 is effected by means of an omnidirectional ball joint 37.

 The tricycle vehicle shown in Figure 30 is still of the swing axle type. Its structure, completely analogous to that of the previous example, will not be described in detail. It will suffice to refer to what has been said with reference to FIG. 29, the same reference numbers having been chosen to designate similar elements.

 A first difference is that the main axle 1 and one-piece auxiliary axle 5 are made integral with one another by coupling bars 46 articulated on the axles, which include footrests 47 for use. of the driver. By these footrests, the driver can possibly act on the inclination of the wheels.

 A second difference is due to the fact that the side bars 2 (whose sketch line is 2a) themselves play the role of rocket carrier.

 It will be noted, with regard to the embodiments of FIGS. 27, 29 and 30, that the main axle should be understood to mean the axle supporting the weight of the vehicle, that is to say the one containing the suspension elements (torsion bars 29, 30) or the one on which the suspension elements are supported (spring 27). The auxiliary axle contains a torsion bar playing an anti-roll effect.

Referring to Figure 31, a tri vehicle
sport cycle has a body attached to a
floor following a rigid assembly forming the axle
main 1 which is here in the lower position, the axle
auxiliary 5a, 5b being in the upper position. Of
knee rests 48 are provided for the pilot whose
seat 49 form with the mechanical assembly, which was
so far called the "vehicle".

Bars 5a, 5b forming auxiliary axle
are articulated at one of their ends by omnidirectional ball joints 37 at two close points integral with the vehicle. At their end, they are articulated by ball joints 37a on lateral bars 2 integral with the wheel-carrying arms 3 which are themselves articulated on the assembly forming the main axle, the line of which has been shown, thanks to nuts 28.

 The wheel-carrying arms 3 swiveling in the nuts 28 are mounted converging towards a point K in order to obtain an induced steering effect under the conditions described above.

 The elastic suspension is obtained by elastic jacks 32 secured on the one hand to the bodywork and on the other hand to the levers 31 carried by the nuts 28.

 Referring to Figure 32, a tricycle cart is of the swing axle type. The main axle, in the lower position, consists of a hoop 1, and the auxiliary axle (not shown) is in two articulated parts. The lateral bars 2 have yokes 24 in which the nuts 28 pivot, the axes of which converge towards a center of drift K. On these bars are articulated wheel-carrying arms 3, one end of which forms a lever 31 coming to bear on an elastic jack 32 also secured to the arch 1.

 With reference to FIG. 33, a quadricycle agricultural tractor comprises two sets of wheels connected to the vehicle by suspension systems with oscillating axles. Each system comprises a main axle 1 in the low position and an auxiliary axle 5a, 5b in two parts. These axles are joined by side bars 2, the sketch line of which is shown in 2a.

 The two main axles 1 are connected to each other by lateral coupling bars 53 articulated on said axles. These coupling rods are connected to respective jacks 54 which are fixed to the vehicle, thus allowing independent travel of the front and rear axles, either on a manual control of the driver, or on the control of a servo device.

 The self-stabilizing characteristics of the independent axles can be modified according to the working conditions by the addition of track spacers 55 which have the effect of increasing the torques at the wheels and therefore the stress forces at the axles. oscillating.

 The quadricycle car shown in Figure 34 is similar to the tractor in Figure 33 and will not be described in detail. The main axle is made flexible by an embodiment in two parts la, lb articulated and provided with a leaf spring 56. On the other hand, the two parts 5a, 5b of the auxiliary axle are joined by a shock absorber 57.

 FIG. 35 shows a tripod vehicle intended to operate on snow. The suspension is of the pendulum type in the high position. The pendulum it is articulated at the upper ends of the lateral bars 12 whose lower ends are articulated on the longitudinal bars 15, themselves articulated at their front end on an axis 16 transverse to the plane of symmetry of the vehicle.

 The support members are skis 14 fixed to the bars 15 by means of leaf springs 58 ensuring the elasticity of the suspension.

 The vehicle can advantageously be fitted with a propulsion system 59.

 With reference to FIG. 36, a low trailer with two wheels is specially designed to be attached to a bicycle tractor vehicle. The trailer arm 61 carries a yoke 62 with a vertical axis which forces the trailer to follow the variable inclinations of the bicycle tractor vehicle. The suspension is of the balanier type in the low position, the load platform playing the role of the pendulum 11. On this platform are articulated the side bars 12 where the longitudinal bars 15 are themselves articulated pivotally mounted around a axis 16 perpendicular to the trailer arm.

 Steering knuckles 3 are articulated on the longitudinal bars 15 and include a lever 63 acting on an elastic belt 64 to ensure the elasticity of the suspension.

 Such a trailer could also be coupled to vehicles such as those described above.

 With reference to FIG. 37, a tricycle vehicle of the sand yachting type comprises a suspension system with oscillating axles consisting of a main axle 1 in the low position and an auxiliary axle 5a, 5b in two parts. These axles are joined at their ends by lateral bars 2 (whose relief line is 2a) to which the wheels 4 are fixed.

 A mast 65, carrying a sail 66, is articulated around an axis 67 directed in the direction of advance of the vehicle. Two elastically compressible shrouds 68 are connected on the one hand to a point of the mast located at a certain height and on the other hand to levers 69 forming part of the side bars 2.

 In the absence of wind, the elastic shrouds 68 balance their thrust on the levers 69, which forces the wheels and the entire structure to adopt the vertical position. Under the thrust of a side wind, the thrust of the shrouds is asymmetrical, which has the effect of tilting the wheels and the whole structure in the direction of the counter-cottage.

 When the vehicle approaches an obstacle in lateral gradient, the same phenomenon occurs. The mast tilts downstream, while the wheels tilt upstream, straightening the structure to oppose the roll.

 FIG. 38 shows a trimaran ship the suspension of which is of the oscillating axle type. The auxiliary axle 5 is constituted by the central beam connecting the floats to the hull, and the main axle is split along the two front and rear beams i, 1 '. The floats constitute both the support members and the side bars 2, shown diagrammatically in 2a along their line of drawing.

 Thanks to the elastic shrouds 68 and to the articulated mast 65, the results obtained are substantially the same as in the case of sand yachting.

 Of course, the invention is not limited to the examples described, but covers any variant accessible to those skilled in the art. One could conceive any other combination of the various suspension elements described, and apply the suspension system to any kind of vehicle.

Claims (26)

 1. Suspension system for a vehicle resting on a support surface (S) by tilting support members (4,14) such as wheels constituting at least one symmetrical pair, at rest, with respect to the longitudinal plane of symmetry (Q) of the vehicle, comprising a main carrying axle (1,11) articulated on the vehicle in the middle and two lateral bars (2,12) articulated at the ends of the axle (1,11) directed transversely to the surface d support and to which the support members are fixed, characterized in that, the vehicle being at rest on a horizontal support surface, each side bar (2.12) constitutes one side (AD) of a trapezoid (ABCD ) one base (AB) of which consists of one half of the main axle (1.11) and the other base (CD) of which is carried by a line joining the ends of the side bars (2.12) together articulated at the ends of the main axle, the side (BC) of the trapezoid opposite the side bar (2,12) being secured to the vehicle.  2. System according to claim I, characterized in that each end of the side bars (2) not connected to the main axle (1) is connected to the vehicle by an auxiliary axle (5) articulated in its middle on the vehicle according to an axis contained in the longitudinal plane of symmetry (Q) of the vehicle.  3. System according to claim 2, characterized in that the auxiliary axle is articulated and consists of at least two axle bars of equal length (5a, 5b).  4. System according to claim 3, characterized in that the auxiliary axle comprises an intermediate bar (5c) rotatably fixed on the vehicle at the ends of which articulate bars (5a, 5b) forming the lateral parts of said auxiliary axle .  5. 5. System according to claim 1, characterized in that the vehicle comprises an intermediate piece (50) rigidly fixed on it, at the ends of which are articulated along axes parallel to the longitudinal axis of the vehicle bars d 'equal length (5a, 5b) forming an auxiliary axle and connecting the ends of the side bars (2) not articulated at the ends of the main axle.  6. System according to claim 1, characterized in that the ends of the lateral bars (12) not connected to the main axle (11) are respectively connected to longitudinal bars (15) themselves articulated on a common axis ( 16) transverse to the longitudinal plane of symmetry (Q) of the vehicle.  7. System according to claim 6, characterized in that the support members (14) are fixed to the side bars via the longitudinal bars (15).  8. System according to one of claims 1 to 7, characterized in that the main axle (1,11) is located above the side bars (2,12).  9. System according to one of claims 1 to 7, characterized in that the main axle (1,11) is located below the side bars (2,12).  10. System according to one of claims 1 to 9, characterized in that it comprises means for modifying the orientation of the support members (4) around an axis substantially perpendicular to the path (T) of the support member on the support surface (S) as a function of the inclination of these members relative to the support surface (S).  11. System according to claim 9, characterized in that it comprises rods (23) articulated on the one hand to one of the axles and on the other hand to supports (22) of the support members (4 ) rotatably mounted on the side bars (2).  12. System according to claim 10, characterized in that the lateral bars (2) carrying the support members (4) are rotated motjes at one of their ends on supports (28), the axes of rotation of these supports converging, when the vehicle is at rest on horizontal ground, towards a point (K) located in the longitudinal plane of symmetry (Q) of the vehicle on the side of the end of the vehicle opposite the end where the support members (4) and above the connection of these supports with the lateral bars with respect to the support surface (S).  13. System according to one of claims 1 to 12, characterized in that the support members (4,14) are fixed to the side bars (2,12) by means of elastic means.  14. System according to one of claims 1 to 12, characterized in that the main axle (1) is resiliently flexible.  15. System according to claim 14, characterized in that the elastically flexible main axle is articulated and consists of at least two axle bars of equal length (la, lb).  16. System according to claim 15, characterized in that the elastically flexible main axle comprises an intermediate bar (tic) rotatably attached to the vehicle at the ends of which articulate bars (la, lb) forming the lateral parts of said elastically flexible main axle.  17. System according to claim 12, characterized in that each support (28) of the side bars (2) carrying the support members (4) comprises a lever (31) compressing a spring (32) which is supported on the main axle (1).  18. System according to one of claims 3, 4, 15 or 16, characterized in that it comprises compression springs (35) mounted between the central part of one of the axles and the lateral parts of the other axle.  19. System according to one of claims 1 to 18, characterized in that at least one of the axles comprises torsion bars.  20. Tricycle vehicle comprising a pair of support members (4,14) connected to the vehicle by means of a suspension system according to one of claims 1 to 19.  21. Vehicle according to claim 20, characterized in that the main axle (1) consists of a vehicle floor.  22. Vehicle according to claim 20, characterized in that the wheels (4) are connected to the side bars (2) by levers (3,31) articulated on these bars and acting on compression springs (32) supported on a hoop (1) forming the main axle.  23. Vehicle according to claim 20, characterized in that the support members (14) are pads connected to the suspension system by leaf springs (58).  24. Vehicle according to claim 20, comprising a sail propulsion system (66), characterized in that the side bars are connected to the mast (65) by means of guy wires (68) of variable length provided with springs of compression.  25. Quadricycle vehicle, comprising two suspension systems according to one of claims 1 to 19, characterized in that it comprises coupling bars (53) of the two systems together, these bars being connected by the articulations to operating cylinders (54).  26. A vehicle with a pair of wheels, forming a trailer for a bicycle tractor vehicle, and comprising a suspension system according to one of claims 1 to 19, characterized in that the main axle (11) consists of a flat loading form, and in that the attachment means (62) to the towing vehicle are arranged to make the trailer follow the inclination of the towing vehicle relative to the bearing surface.