FR2726791A1 - IMPROVEMENTS TO A PASSIVE CONTROL SYSTEM OF THE PRE-STRESSING OF THE SUSPENSIONS OF A VEHICLE - Google Patents

Abstract

A passive, self-contained mechanical control device for controlling the preloading of vehicle suspensions (1) depending on the static and dynamic loads thereon, wherein each suspension (1) comprises a hydraulic cylinder (3) between the housing (26) of the suspension (1) and the body of the vehicle. The hydraulic cylinders (3) are interconnected and biased via hydraulic circuits (5) by a hydraulic accumulator (66) containing a spring (38) with a constant preload applied to the various circuits (5) by a piston (9b). The circuit (5) in each control device is separate from the other circuits (5) and the hydraulic accumulator (66) comprises a working chamber (10) for each hydraulic cylinder (3). Each suspension (1) comprises at least one resilient member with at least one abutment restricting operation to one portion of the member. The device may advantageously be used in racing vehicles.

Description

 The present invention relates to a mechanical, autonomous and passive control device for the prestressing of vehicle suspensions.

 It provides optimal grip for all types of vehicles it equips, and more particularly racing vehicles.

 The search for the efficiency of suspensions in competition in the sixties was focused on optimizing suspension drawings combined with the use of great flexibility allowing the tires to be used to their full potential.

 These cars were fitted with narrow tires and had no aerodynamic downforce.

 An unquestionable grip was obtained taking into account the performance of the tires of the time, but this was only usable at low and medium speed because the roll and pitch made the vehicle enter into a rocking movement at the slightest imbalance, which prohibited approaching the grip limit.

 Gradually, the adoption of aerodynamic downforce and the evolution of tires have diminished the importance of the role of suspension drawings.

 These supports required an increase in suspension stiffnesses and, consequently, a reduction in travel.

 The current predominance of aerodynamics in competition places designers facing a dilemma concerning the maximum exploitation of tires.

 On the one hand, the aerodynamic supports loading the tires considerably increase their grip potential, but on the other hand, these supports require constant wedging obtained by stiffening the suspensions which then become incapable of ensuring their absorption role. The tires then work under very unfavorable conditions.

 For this reason, so-called active suspensions, that is to say dissociating the aerodynamic setting from the stiffness of the suspensions, have appeared.

 They are now prohibited in competition.

 It was therefore necessary to increase the aerodynamic load, and therefore the stiffness of the suspension ions to increase the adhesion potential.

 However, a stiffer car with less suspension travel is more difficult to drive, because the reactions are more lively and less noticeable, the grip limit being difficult to approach.

 These problems can also be encountered with production vehicles.

 The object of the invention is to interconnect the operation of all the suspensions of a vehicle so that it undergoes at least the perverse effect of static and dynamic loads.

 The state of the art includes numerous documents which describe devices for adjusting the attitude of a vehicle.

 Document WO-A-8,904,262 relates to a suspension system for a vehicle comprising an elastic suspension means, for example an anti-roll torsion bar common to at least two vehicle wheels, a means for adjusting the elastic suspension means in order to modify its load, a means for detecting the acceleration of the vehicle and a means for measuring the adjusted position of the elastic suspension means. The system further comprises control means reacting to the acceleration of the vehicle in order to determine the necessary adjustment of the elastic suspension means, and to adjust it until the required adjustment is obtained.

 The document FR-A-2.633.564 provides a servo drive for the hydraulic suspension of the wheels in vehicles. The servo is intended to adjust changes in the characteristics of the vehicle suspension. This servo control allows you to modify the height of the suspension as well as the rigidity of the vehicle suspension. In addition, the servo drive causes dynamic loads from one wheel to be transmitted to other wheels on the vehicle. It also includes four hydraulic spring devices assembled with the four wheels of this vehicle. A hydraulic pump has a hydraulic connection with these devices. There are also hydraulic connections between the hydraulic transmitters and the hydraulic spring devices.

 Document FR-A-2,663,267 relates to a double-acting cylinder which is interposed between the vehicle body and each of the wheels, each cylinder comprising a body and a piston secured respectively to the suspended mass of the vehicle and to a wheel support, the piston dividing the cylinder body into a first chamber connected to a pressurized fluid accumulator and a second chamber traversed by a rod secured to the piston and mechanically coupled to a wheel support. The suspension comprises conduits for applying the pressure of the fluid prevailing in the first chamber of each cylinder, in the second chamber of the cylinder associated with the other wheel of the same set of wheels. The suspension further comprises a balancing device consisting of '' a double piston comprising a first and a second stage sliding in chambers of corresponding sections, and conduits for transmitting the fluid pressures of the accumulators associated with the jacks of the two diagonals of the two-sided suspension of the first and second stages of the double piston , respectively, on which these pressures act in the same direction so as to ensure the isostatism of the suspension.

 In these documents, electronic interventions are necessary, these suspensions can be considered as semiactive. In addition, hydraulic circuits are coupled between the suspensions.

 The document EP-A-0.398.804 relates to a suspension device which comprises a hydraulic cylinder associated with each of the wheels of a vehicle and interposed between an arm of the wheel and the body of the vehicle, the two wheels of the axle front and one of the two wheels of the other axle each being equipped with a height corrector, and the fourth wheel being equipped with a slide valve controlled by the pressures of the four jacks, this device being characterized in that the piston of the hydraulic cylinder associated with each wheel is constituted by at least one coil spring which instantly collects the relatively short deflections of the suspension by resting on the volume of hydraulic fluid in the cylinder which behaves like a hydraulic shim with variable volume .

 This mechanism is a simple height corrector of the vehicle trim.

 The present invention provides a fully mechanical, autonomous and passive servo device which synchronizes the movement of the suspension support shirts as a function of the static and dynamic loads undergone by the vehicle, where the device is installed.

 To this end, the invention relates to a mechanical, autonomous and passive servo-control device for prestressing the suspensions of a vehicle, as a function of the static and dynamic loads undergone by it, where each suspension, associated with a wheel of the vehicle, comprises a hydraulic cylinder, interposed between the support jacket of said suspension and the body of said vehicle, which acts on said jacket in order to vary the preload of the suspension; all the jacks are connected and stressed via hydraulic circuits containing a first fluid, by a hydraulic accumulator containing a spring, the constant preload of which is applied to the various hydraulic circuits by means of a main piston, the hydraulic circuit of each servo-control device is independent of all the other circuits, and the hydraulic accumulator comprises a working chamber per cylinder, each chamber containing a piston mechanically integral with the main piston of said accumulator, so that the movements of the support liners suspensions are synchronous whatever the static and dynamic loads undergone, the liners determining a self-stabilizing reference level, characterized in that the hydraulic accumulator consists of two separate parts, on the one hand, the hydraulic spring and, d on the other hand, the working chambers; these two parts are connected to each other, in leaktight manner, by at least one hydraulic circuit containing a second fluid, and that the device comprises means for interrupting the movement of the second fluid in the hydraulic circuit as a function of the load carryovers suffered by the vehicle.

 The hydraulic spring is connected to the working chambers by means of two hydraulic circuits and the means for interrupting the second fluid acts only on one of the circuits.

 On the one hand, each circuit includes a non-return valve, one authorizing the movement of the second fluid from the spring towards the chambers, the other authorizing the reverse movement, and on the other hand, the means of interruption acts on the circuit provided with the valve authorizing the movement of said second fluid from the chambers to said spring.

 The hydraulic circuit check valve is located upstream of the interrupting means.

 According to a first embodiment, the interruption means consists of an extension of each hydraulic circuit, via one of the working chambers, in the direction of a mechanical means, actuable by the first fluid and capable of preventing the passage of the second fluid in the hydraulic circuit.

This interruption means is constituted by a box which comprises
- a longitudinal bore placed in the longitudinal extension of the pipe for the passage of the second fluid,
- a transverse bore per working chamber, and
- a piston movable longitudinally in each transverse bore.

 First of all, each mechanical means is constituted by the transverse bore serving as a chamber for the piston mounted against, on one side, a spring and, on the other side, the first fluid coming from the extension of one of the hydraulic circuits; then, each piston has a throttle and / or a bore, perpendicular to the axis of the piston, which allows (tent) or not the passage of the second fluid according to the forces exerted, on one side, by the first fluid and, the other side, by the spring as a function of the load transfers undergone by the vehicle.

 According to a second embodiment, the interruption means is constituted by a drawer actuated mechanically by an actuating lever which comprises, on the one hand, an axis of rotation, and, on the other hand, a counterweight allowing the rotation of the lever around its axis according to the transverse load transfers undergone by the vehicle and the movement of the slide capable of preventing the passage of the second fluid in the hydraulic circuit.

 The lever comprises means for returning to position, such as self-centering springs.

 This lever is connected to the drawer by a link constituting the rod of a shock absorber.

 The attached drawings are given as indicative and non-limiting examples. They represent two preferred embodiments according to the invention. They will allow the invention to be easily understood.

 Figure 1 shows a partial longitudinal sectional view of all the elements constituting the passive and improved servo device, which comprises one of the suspensions, the accumulator, consisting on the one hand of the chambers and on the other hand of the spring main gas, and a first embodiment of the means for interrupting the fluidic movement.

 2 shows a cross-sectional view of the interrupting means according to A-A of Figure 1, the fluid movement is not interrupted.

 FIG. 3 represents a view identical to that of FIG. 2, in which the fluidic movement is interrupted.

 FIG. 4 represents a view in partial longitudinal section of a second embodiment of the means for interrupting the fluidic movement.

 Finally, Figure 5 shows a partial longitudinal sectional view of a suspension whose structure and technical characteristics are particularly advantageous for the present invention.

 The present invention can be used for all types of suspensions.

 However, it is particularly advantageous for suspensions as described and claimed in patent applications EP-A-0.466.628, EP-A-O.446.338 and EP-A-0.520.928 of the applicant.

 This invention is also an improvement on the patent application FR 94/13866 of the applicant.

 These "CONTRACTIVE" (registered trademark) suspensions which are the subject of these four patent applications cited above, have the characteristic of providing the vehicle, on which they are installed, with a suspense whose stiffness is greater in the race. situated between the position in "load running order" and the position "wheel hanging" only in the race lying between the position "load running order" and the position "suspension crushed until impact stops".

 To simplify, the CONTRACTIVE suspension is characterized by the existence of greater stiffness in the "rebound" race than in the "shock" race.

 When the stiffness curves are represented graphically, it can be observed that this change in stiffness results in a slope break.

This break in slope, positioned in the vicinity of the position in "load operating order", is at the origin of the remarkable attitude stability provided by the suspension.
CONTRACTIVE to the vehicle on which it is installed.

 However, other problems have arisen.

 Thus, aerodynamics requires constant timing.

 This results in an increase in the vertical stiffness of the suspension, which decreases the absorption capacity of the suspensions, the reactions of which are less perceptible.

 In addition, planing is not acceptable. It requires increasing the anti-roll values. The trains are then more rigid and motor skills are sacrificed.

 The CONTRACTIVE suspension is characterized by two distinct stiffnesses between the compression stroke and the rebound stroke, the ratio of these compression-rebound stiffnesses being of the order of one for three.

 With the vehicle traveling at constant speed and in a straight line, these suspensions work in a so-called "connection" zone between the low compression stiffness and the large rebound stiffness.

 During a longitudinal or transverse acceleration, the loaded suspensions will work in the zone of low stiffness while the discharged suspensions will work in the zone of great stiffness, which has the effect of opposing the taking of pitch or roll .

 During a shock loading of a suspension, it passes into the zone of low stiffness and absorbs the obstacle.

 The CONTRACTIVE suspension therefore offers a stiffness that introduces asymmetrical roll and pitch.

 It allows most of the overall deflection caused by acceleration to be transferred to the benefit of the support suspension.

 This allows, for an equivalent attitude, to benefit from greater compression flexibility, which promotes vertical absorption, lowers the center of gravity during rests and improves the perception of the reactions of the car.

 The combination of the CONTRACTIVE suspension with the new servo system allows a connection zone between the two stiffnesses, which adjusts automatically according to the attitude of the vehicle when it is not subjected to acceleration .

 Thus, each suspension will oscillate between the two distinct stiffnesses around this connection zone.

 Whether for a production vehicle, or a fortiori for a competition car, the attitude is not constant due to the static (fuel) and above all very variable aerodynamic loads that it undergoes. The connection area then moves according to this attitude, thus adjusting the self-stabilizing reference level.

 This is achieved by a mechanism described below.

 This invention relates essentially to an adaptation of the CONTRACTIVE suspension to competition cars, and in particular to single-seaters.

Principle of the connection area
The connection zone between the two stiffnesses is regulated by a stop and must always be in the zone corresponding to the attitude of the vehicle not subjected to acceleration.

 Thus, any suspension movement will oscillate between the two distinct stiffnesses, around this connection zone.

 Unfortunately, the attitude of a competition vehicle, such as a Formula 1, is not constant, due to the static (fuel) and above all very variable aerodynamic loads that it undergoes. It is then necessary to move the connection area according to this plate, which is easy thanks to a simple automation.

 However, this automatism, due to the intervention of an electronic module, is incompatible with the current Formula 1 regulations.

Load-dependent prestressing stops (BPAC)
It was necessary to imagine a fully autonomous and passive system making it possible to control the position of the connection zone to static and aerodynamic loads.

 This system works according to three principles.

 First there is MOBILITY, in which the connection stops are mobile and are positioned according to the height of the single-seater, helped by a low hydraulic preload.

They thus move the connection area according to the vehicle load.

 Then there is the INTERDEPENDENCE, in which the connection stops are interdependent, in their movements.

Thus they are synchronized so as to always be placed in the same relative position with respect to each other, this guaranteeing an identical positioning of the four connection zones.

 Finally, there is the STRATEGY, in which the displacement of each stop is only possible if the four suspensions compress or relax simultaneously, under the effect of a load variation. In other words, any mass transfer generated by a transverse or longitudinal acceleration, having opposite effects on the suspensions, will block the stops in the position dictated by the attitude of the vehicle before this change of state. On the other hand, a variation of aerodynamic load generated by a variation of speed will act on the four suspensions in the same direction, which will authorize a simultaneous displacement of the stops which will thus catch up with the new static position of the suspensions.

Obtaining the three operating principles of BPAC
With regard to MOBILITY, the connection stops, which have become prestressing abutments controlled by the load, are hydraulically loaded by a gas spring providing them with constant prestressing of the order of 25 kg each, in the same way as a servo -brake acts on pistons via a hydraulic fluid. BPACs will thus be able to move the connection area, pushed by this preload in one direction, and by the suspension itself in the other direction.

 With regard to INTERDEPENDENCE, the BPACs are made dependent on each other by the use of a master cylinder between the gas spring and these. The master cylinder or working chamber 10 of the accumulator 66 controlling the hydraulic fluid only authorizes identical flow rates between the four stops, making a variation in positioning between them impossible.

Regarding STRATEGY, the hydraulic circuit of a
BPCA has two states. The first corresponds to the stop in action, undergoing a load of 25 kg (suspension at the limit of the connection area) or more (suspension in great stiffness resting on the stop). This state is characterized by a pressure greater than or equal to the initial precharge pressure.

The second state corresponds to the cleared stop (suspension in low stiffness), which generates a pressure drop in the hydraulic circuit of the BPCA. It then suffices to control the movement of the master cylinder by a hydraulic unit connected to the four BPAC circuits, which will block any flow as soon as a pressure drops below the initial preload threshold. This drop in pressure indicates that one, two, or three suspensions go into compression stiffness and therefore that a mass transfer or the absorption of an obstacle is taking place, which will block the BPAC in their position. respective. On the other hand, if all the pressures drop, this indicates a lowering of the vehicle due to an increase in load, the system then authorizes the four BPAC to move to catch the new position.

How BPAC works
When the vehicle undergoes load variations without mass transfer, the four suspensions act in the same direction and the BPACs, forced by their preload, follow the upward or downward movement of the body. They thus move the connection area according to the vehicle load.

 During longitudinal or lateral acceleration, suspensions collapse and others relax. The BPAC of the suspensions in the compression phase will lose their prestress. The resulting pressure drop will block any movement of the master cylinder through the action of the hydraulic control unit.

We will thus make the vehicle work with a
CONTRACTIVE SUSPENSION, the connection area of which will be ideally positioned according to the load, then will be blocked as soon as a mass transfer occurs.

 With this system, each suspension will work at great stiffness on the rebound stroke and at low stiffness on the shock stroke, the tipping point between these two stiffnesses, called "connection zone", positioning itself automatically at the "static" level of the vehicle, that is to say the attitude determined by the static and aerodynamic load, before the appearance of a transfer generated by braking, acceleration, or turning.

 This mechanism is fully autonomous and passive and allows the position of the connection area to be controlled by static and aerodynamic loads.

 Each suspension 1 is associated with a wheel of a vehicle and comprises a hydraulic cylinder 3 which is interposed between the suspension 1 and the body of the vehicle, not shown in the figures. Each suspension 1 includes a bleed screw 19.

 Each hydraulic cylinder 3 is formed of a jacket 26, forming a cylinder, in which is contained the upper cup 4 for supporting the lifting springs, forming a piston.

The shirt 26 is movable relative to said cup 4, itself secured to the body via the upper attachment point 17 of the suspension 1 on said body.

 The displacement of the jacket 26 makes it possible to vary the preload which is applied to the suspension 1.

 The set of jacks 3 is connected and controlled hydraulically via the hydraulic circuits 5, clearly visible in FIG. 1, by a hydraulic accumulator 66, which contains a gas spring whose constant prestressing pressure is applied to the various hydraulic circuits 5 by l 'Intermediate of a main piston 9b, via the hydraulic circuits 27 and 28.

 So that the movement of the support liners 26 of the suspensions is synchronous, whatever the static and dynamic loads undergone by the vehicle, the hydraulic circuit 5 for controlling each hydraulic cylinder 3 is independent of all the other circuits 5.

 In addition, the hydraulic accumulator 66 comprises a working chamber 10 per cylinder 3.

 Each chamber 10 contains a piston 11 mechanically integral with the main piston 9b of the accumulator 66.

 In fact, said accumulator 66, under the effect of a gaseous main spring 38, will make it possible to apply a thrust to all of the pistons 11 contained in the working chambers 10.

 The oil contained in the accumulator 66 is referenced 39.

This force is transmitted, using the hydraulic circuits 5, towards the hydraulic cylinders 3 of the suspensions 1, and more precisely towards the liners 26 which can move, according to
F3, compared to the cups 4.

 The oil 22 contained in the hydraulic circuit 5 being incompressible, the thrust of the main spring 38 will cause the pistons 11 to move inside the chambers 10, which will cause the oil 22 to move.

 This movement of oil 22 will find its outcome at the level of the jack 3 where the oil 22 will act on said support shirts 26, according to arrow F3 in FIG. 5.

 The CONTRACTIVE suspension is well represented in this figure 1.

 It comprises an upper fixing point 17 of the suspension 1 on the body and a lower fixing point 16 of the suspension 1 on the suspension arm.

 Very conventionally, the suspension 1 also has a shock absorber 18, a main spring 12 and an auxiliary or opposing spring 13, the two springs being separated by a support cup 24.

 Each suspension 1 also comprises a means 23 for adjusting the height of the body or ground clearance.

 The movement described according to arrow F3 can, of course, be carried out in the opposite direction.

 As can be seen in FIG. 1, the working chambers 10, which are each supplied by a hydraulic circuit 5, are placed in the longitudinal extension of each other.

 In the embodiment of FIG. 1, the piston of the working chamber 10, closest to the spring 38 of the accumulator 66, also acts as the main piston 9b of said accumulator 66.

 In practice, the servo device operates according to two principles.

 First of all, the liners 26, containing the upper cups 4, are movable and are positioned according to the height of the vehicle under the action of the prestressing. Then the movements are dependent on each other.

 Thus, displacements are possible only if the four suspensions compress or relax simultaneously.

 The liners 26 are therefore hydraulically pushed by a gas spring 38 providing them with a constant prestress of the order of 25 kilograms each. This value is an example of what can be used for a competition car.

 The liners 26, containing the upper cups 4, will therefore move the connection zone following the attitude of the vehicle.

 The movements of the sleeves 26 will be dependent on the use of an accumulator 66 which controls the hydraulic fluid 22 and only authorizes identical flow rates between the jacks 3, which will therefore balance out.

 When the vehicle undergoes load variations without mass transfer, the four suspensions 1 act in the same direction and the jacks 3, forced by their preload, follow the upward or downward movement of the body.

 They thus move the connection area and the inflection point according to the vehicle load.

 During longitudinal or transverse acceleration, suspensions collapse and others relax.

 Assuming that the mass transfer does not exceed the sum of the prestresses (100 kilograms), the jacks 3, wanting to descend, will oppose the jacks 3, wanting to go up, and will balance, no opposing movement being compatible with hydraulic accumulator 66.

 In this case, the vehicle has suspensions that work like a CONTRACTIVE suspension, the connection area of which will be adequately positioned according to the load, then will be blocked when a mass transfer occurs.

 With this servo device, each suspension 1 works in great stiffness on the rebound stroke and the first twenty five kilograms of the compression stroke, then in slight stiffness over the rest of the shock stroke.

 A car equipped with CONTRACTIVE suspensions, provided with such jacks 3, permanently exhibits an extremely high stiffness promoting high efficiency, but in contrast to a conventional suspension, of the sport type, that is to say stiff, when the impact exceeds a thrust of 25 kilograms, the suspens ion 1 then leaves its zone of very stiffness to enter the zone of low stiffness, which makes it possible "to erase" the projection of the track without unbalancing the car.

 This mechanical system is therefore fully automatic and requires neither control nor external energy, the suspension adjusting itself.

 However, when one of the suspensions 1 undergoes a pressure greater than the pressure of the main spring 38, the piston 9b or 11 which undergoes the thrust will cause the other pistons 9b and / or 11 in its movement, which will be detrimental for the handling.

 To eliminate these risks, the accumulator 66 consists of two dissociated elements, on the one hand, the gaseous main spring 38 and, on the other hand, all of the working chambers 10 of said accumulator 66.

 These two parts 38 and 10 are connected to each other by two hydraulic circuits 27 and 28, well represented in FIG. 1.

 These hydraulic circuits 27 and 28 are intended to allow the incorporation into this system forming the accumulator 66, of a means 30 for interrupting the movement of the fluid 39 between the chambers 10 and the main spring 38.

 Thus, the hydraulic circuit 28 comprises a housing 32 which contains a longitudinal bore 33 passing through it and which allows the passage of the fluid 39 from one end to the other of the housing 32.

 This longitudinal bore or channel 33 can be interrupted due to the transverse actuation in transverse bores 34 of pistons 31.

 As can be seen in Figures 2 and 3, these pistons 31 have a head provided with a seal 49 for separating the oil 22 from the hydraulic circuits 5 extending in the form of a hydraulic circuit 35 between the chambers 10 and the housing 32.

 In fact, depending on the pressure applied to the cylinders 3 of the suspensions 1, the oil 22 will penetrate into the chambers 10 and then will be transported using the hydraulic extension circuit 35 to the housing 32 where the oil will being able to penetrate, according to F4 of FIG. 2, or to go out, according to F5 of FIG. 3 and thus actuate in compression the piston 31 against a spring 36.

 As can be seen in FIG. 2, the piston 31 has a constriction 37 which allows the passage of the fluid 39 when the latter, as is the case in this figure, is located in the extension of the longitudinal bore 33, represented by dotted because placed behind said piston 31.

 When the pressure of the fluid 5 is released, the spring 36 will move the piston 31 downward, as is the case in FIG. 3, and the channel 33 will no longer be able to allow the passage of the fluid 39 due to the presence of the skirt 50 of the piston 31. This skirt 50 has a compression movement which is limited by a shim 48. The spring 36 is positioned between the skirt 50 and the shim 48.

 It is therefore easy to understand that the pistons 31 have a transverse movement relative to the longitudinal channel or bore 33, which will make it possible, depending on the pressure conditions prevailing at the level of the head of the pistons 31, to cut or allow passage fluid 39 inside said channel 33.

 In order to allow correct operation of the interruption means 30, each hydraulic circuit 27 and 28 includes a non-return valve 29, the non-return valve 29 of the hydraulic circuit 28 allowing the movement of the fluid 39 only from the chambers 10 towards the spring. main gas 38. The other hydraulic circuit 27 comprises a non-return valve 29 which allows the passage of the fluid 39 only from the spring 38 to the chambers 10.

 Therefore, the passage of the fluid or oil 39 is forced.

 In the particular embodiment of FIG. 1, the interruption means 30 acts on the circuit 27 provided with the valve 29 authorizing the movement of the fluid 39 from the chambers 10 towards said spring 38.

 In addition, the non-return valve 29 of the hydraulic circuit 28 is located upstream of the interruption means 30.

 The interruption means 30 is constituted by an extension circuit 35 of each hydraulic circuit 5 via one of the working chambers 10 in the direction of a mechanical means actuable by the fluid 22 and capable of preventing the passage of the fluid 39 in the hydraulic circuit 27, this mechanical means being constituted by the transverse bore 34 serving as a chamber for the piston 31 mounted against a spring 36 on the one hand, and of the fluid 22 on the other hand, the fluid 22 coming from the hydraulic extension circuit 35 of one of the hydraulic circuits 5.

 At the level of the chambers 10, it is of course necessary that the point of arrival of the hydraulic circuit 5 and the point of arrival of the hydraulic circuit 35 of each chamber 10 are located opposite so that there there is no possibility for the pistons 11 to come to prevent the free circulation of the oil or fluid 22 between the two fluid circuits 5 and 35.

 The piston 31 is therefore moved according to the forces exerted on one side by the fluid 22, and on the other side by the spring 36 and this, according to the load transfers undergone by the vehicle.

 In another embodiment, the interruption means 40, shown in FIG. 4, consists of a drawer 41 mechanically actuated by an actuating lever 42 which comprises on the one hand, an axis of rotation 43 and on the other hand, a counterweight 44 allowing the rotation of the lever 42 around the axis 43, such as a ball joint.

 The displacement of the drawer 41 takes place according to F8 or F9 depending on whether the tilting of the lever 42, under the effect of its counterweight 44, takes place according to F6 or F7.

 Although this is not shown, the drawer 41 has substantially the same function as the piston 31 of the previous version, that is to say that the drawer 41 may or may not, depending on its position, the passage of oil inside the hydraulic circuit located between the chambers 10 and the accumulator 38.

 When the lever 42 is rotated relative to its ball joint 43 according to F6 or F7, the drawer will prevent the passage of the oil.

 In fact, this embodiment only makes it possible to intervene on the pitching movements of the vehicle during turns.

 However, one could very well imagine another lever having a movement perpendicular to the movement of the lever 42 which can act on braking and / or acceleration.

 Of course, it is also necessary that the lever 42 is held in its proper position allowing the passage of the oil.

 To do this, it is necessary to associate with the lever 42 return means in position such as self-centering springs 45.

 Similarly, to avoid, during sudden movements, rocking of the lever 42 which would be detrimental to the stability of the vehicle, the lever 42 is connected to the drawer 41 by a link 46 which constitutes the rod to the damper 47.

REFERENCES
1. Suspensions
3. Hydraulic cylinders
4. Upper support cups forming pistons of the cylinders 3
5. Hydraulic circuits 9b. Main piston of accumulator 66 10. Working chambers of accumulator 66 11. Pistons of chambers 10 12. Main spring of suspension 1 13. Auxiliary or opposing spring of suspension 1 16. Lower attachment point of suspension on the body 17. Upper attachment point of the suspension on the arm
suspension 18. Shock absorber 19. Bleeding screw for suspensions 1 22. Oil or fluid for circuits 5 23. Means for adjusting the height of the body or ground clearance 24. Support cup 26. Shirts, containing the cups 4, forming the cylinders
cylinders 3 27 and 28. Hydraulic circuits 29. Non-return valve 30. Means of interrupting the movement of the fluid 39 between the
chambers 10 and the main spring 38 31. Movable pistons 32. Housing constituting the means 30 33. Longitudinal bore or channel of the housing 32 through which the
fluid 34. Transversal bores of the housing 32 housing the pistons 31 35. Extension circuits of the hydraulic circuits 5 36. Piston springs 31 37. Throttling of the pistons 31 38. Main gas spring 39. Oil or fluid of circuits 27 and 28 40. Other means of interrupting the movement of the fluid between
chambers and the main spring 41. Drawer 42. Lever for actuating the drawer 41 43. Axle of the lever 42 44. Counterweight of the lever 42 45. Self-centering springs of the lever 42 46. Rod 47. Shock absorber 48. Shims of the pistons 31 49. Piston head seals 31 50. Piston skirt 31 66. Accumulator
F3. Displacement of the chamber or jacket 26 relative to the piston
or cup 4 under the effect of the displacement of the oil 22
F4. Oil inlet 22 in the transverse bores 34
F5. Oil outlet 22 from transverse bores 34
F6 and F7. Lateral movements of the counterweight 44
F8 and F9. Movements of drawer 41 interrupting the movement of
fluid between the chambers and the main spring

Claims (10)

 1. Device for mechanical, autonomous and passive control of the prestressing of the suspensions (1) of a vehicle, as a function of the static and dynamic loads undergone by the latter, where each suspension (1), associated with a wheel of the vehicle , comprises a hydraulic cylinder (3), interposed between the support jacket (26) of said suspension (1) and the body of said vehicle, which acts on said jacket (26) in order to vary the preload of the suspension (1 ); all the jacks (3) are connected and biased via hydraulic circuits (5) containing a first fluid (22), by a hydraulic accumulator (66) containing a spring (38) whose constant prestressing is applied to the various hydraulic circuits (5) by means of a main piston (9b), the hydraulic circuit (5) of each control device is independent of all of the other circuits (5), and the hydraulic accumulator (66) comprises a working chamber (10) per cylinder (3), each chamber (10) containing a piston (11) mechanically integral with the main piston (9b) of said accumulator (66), so that the movements of the support sleeves (26 ) suspensions (1) are synchronous whatever the static and dynamic loads undergone, the liners (26) determining a self-stabilizing reference level, characterized by the fact  that the hydraulic accumulator (66) consists of two separate parts, on the one hand, the hydraulic spring (38) and, on the other hand, the working chambers (10); these two parts are connected to each other, in leaktight manner, by at least one hydraulic circuit (27 and / or 28) containing a second fluid (39), and  that the device comprises a means of interruption (30 or 40) of the movement of the fluid (39) in the hydraulic circuit (27 or 28) as a function of the load transfers undergone by the vehicle.  2. Device according to claim 1, characterized in that  that the hydraulic spring (38) is connected to the working chambers (10) by means of two hydraulic circuits (27 and 28) and  that the means for interrupting (30 or 40) the fluid (39) acts only on one (27) of the circuits (27 and 28).  3. Device according to claim 2, characterized in that  that each circuit (27 or 28) comprises a non-return valve (29), one (29) authorizing the movement of the fluid (39) from the spring (38) towards the chambers (10), the other (29) allowing reverse movement, and  that the interruption means (30 or 40) acts on the circuit (27) provided with the valve (29) authorizing the movement of the fluid (39) of the chambers (10) towards said spring (38).  4. Device according to claim 3, characterized in that  that the non-return valve (29) of the hydraulic circuit (27) is located upstream of the interruption means (30 or 40).  5. Device according to any one of claims 1 to 4, characterized in that  that the interruption means (30) is constituted by an extension (35) of each hydraulic circuit (5), via one of the working chambers (10), in the direction of a mechanical means, actuable by the fluid ( 22) and capable of preventing the passage of the fluid (39) in the hydraulic circuit (27).  6. Device according to any one of claims 1 to 5, characterized in that  that the interruption means (30) consists of a housing (32) which comprises  a longitudinal bore (33) placed in the longitudinal extension of the pipe (27) for the passage of the fluid (39),  - a transverse bore (34) per working chamber (10), and  - A piston (31) movable longitudinally in each transverse bore (34).  7. Device according to claims 5 and 6, characterized in that  that each mechanical means is constituted by the transverse bore (34) serving as a chamber for the piston (31) mounted against, on one side, a spring (36) and, on the other side, fluid (22) coming from the extension (35) of one of the hydraulic circuits (5), and  that each piston (31) has a throttle (37) and / or a bore, perpendicular to the axis of the piston, which allows (tent) or not the passage of the fluid (39) according to the forces exerted, on one side, by the fluid (22) and, on the other side, by the spring (36) according to the load transfers undergone by the vehicle.  8. Device according to any one of claims 1 to 4, characterized in that  that the interrupting means (40) consists of a drawer (41) actuated mechanically by an actuating lever (42) which comprises, on the one hand, an axis of rotation (43), and, on the other hand , a counterweight (44) allowing the rotation of the lever (42) about its axis (43) according to the transverse load transfers undergone by the vehicle and the movement of the slide (41) capable of preventing the passage of the fluid (39 ) in the hydraulic circuit (27).  9. Device according to claim 8, characterized in that  that the lever (42) comprises means for returning to the position, such as self-centering springs (45).  10. Device according to any one of claims 8 or 9, characterized in that  that the lever (42) is connected to the drawer (41) by a link (46) constituting the rod of a shock absorber (47).