CN109070677B

CN109070677B - Hydraulic suspension system for vehicle

Info

Publication number: CN109070677B
Application number: CN201780019607.6A
Authority: CN
Inventors: N·贝林格; F·甘冈
Original assignee: PSA Automobiles SA
Current assignee: PSA Automobiles SA
Priority date: 2016-03-25
Filing date: 2017-03-03
Publication date: 2022-04-01
Anticipated expiration: 2037-03-03
Also published as: EP3433114A1; WO2017162948A1; CN109070677A

Abstract

The invention relates to a hydraulic suspension system for a motor vehicle, comprising: a hydraulic attack stop (9b) by which the piston and the cylinder of which attack the hydraulic stop move relative to each other when the piston of the shock absorber (1b) reaches a first attack stroke; and a mechanical attack stop (7b) which is compressed between the cylinder of the shock absorber and the body of the vehicle when the piston of the shock absorber reaches a second attack stroke in the cylinder of the shock absorber which is greater than the first stroke, the suspension system further comprising a computer (32) which acts on an operating member (30) of the shock absorber (1b) which modifies the level of force generated by the movement of the piston in the cylinder. The invention is applicable in the field of motor vehicle industry.

Description

Hydraulic suspension system for vehicle

Technical Field

The invention relates to a hydraulic suspension system for a vehicle, in particular for a motor vehicle.

Background

As is known per se, for each of the wheels of a vehicle, the hydraulic suspension system of said vehicle, in particular of a motor vehicle, comprises a shock absorber having a piston which is movable in a corresponding cylinder and is interposed between the body and a journal bracket (port-fusee) of the wheel of said vehicle. The function of this damper is to strongly limit the oscillations transmitted by the wheels to the body of the vehicle when they encounter irregularities or obstacles present on the road on which the vehicle is running, and to brake the movements of said body in dynamic actions such as braking and cornering.

In order to limit and brake the travel of the piston of a shock absorber in its compression stroke (also called attack stroke), said shock absorber comprises a compressible mechanical (or optionally hydraulic) attack stop (bute e d' attack). The function of this attack stop is also to protect the chassis of the vehicle in the event of a relatively large axle excursion (d) of the corresponding wheel due to an accident or to a relatively large obstacle (e.g. a herringbone deceleration strip).

A hydraulic attack stop with a piston which is movable in a corresponding cylinder and whose piston is intended to be moved by the piston of the buffer when the latter approaches the end of its stroke is known in particular from document FR 2995048.

However, in the case where the large stroke of the piston of the damper is of a predominantly accidental nature, the comfort of the suspension is not a priority with respect to maintaining the mechanical integrity of the vehicle. For this reason, the attack stop is generally very rigid and generates a discontinuous, sudden force. In these cases, the comfort of the occupants of the vehicle can thus be strongly impaired.

Disclosure of Invention

The object of the present invention is to overcome the above mentioned drawbacks of the prior art.

In order to achieve this object, the invention relates to a hydraulic suspension system for an axle of a vehicle, in particular of a motor vehicle, said hydraulic suspension system being in accordance with claim 1.

Other features are set forth in the dependent claims.

The invention also relates to a vehicle, in particular a motor vehicle, and comprising such a hydraulic suspension system.

Drawings

The invention will be better understood and other objects, features, details and advantages thereof will become more apparent upon reading the detailed description in the specification, given by way of example only, and by referring to the accompanying drawings, which illustrate the prior art and two embodiments of the invention, and in which:

figures 1A and 1B show a longitudinal section of a prior art shock absorber and a graph showing the variation of the force sent by the suspension system as a function of the stroke of the piston of the shock absorber in the cylinder of the shock absorber, respectively;

figures 2A and 2B show a longitudinal section of the steered damper of the suspension system according to the first embodiment of the invention when the vehicle is in a reference steady state and a diagram showing the forces sent by the suspension system corresponding to the position of the piston indicated on figure 2A, respectively;

fig. 3 shows a diagram illustrating different force profiles of a steered bumper of a suspension system according to the invention; and

figures 4A and 4B show a longitudinal section of the steered damper of the suspension system according to a second embodiment of the invention when the vehicle is in a reference steady state and a diagram showing the forces sent by the suspension system corresponding to the position of the piston indicated on figure 4A, respectively.

Detailed Description

With reference to fig. 1A, a hydraulic suspension system of a vehicle, in particular of a motor vehicle, will now be described.

For each wheel of the vehicle, the suspension of the vehicle comprises a hydraulic shock absorber 1 comprising a cylinder-shaped body 2 and a piston 3 movable in the cylinder 2. The damper 1 is interposed between a body 6 of the vehicle and a journal bracket of a corresponding wheel. The piston 3, integral with a first end of a rod 14, the other end of which is coupled to the body 6 of the vehicle, delimits in the cylinder 2 two

chambers

4, 5, respectively compression and decompression chambers, between which the incompressible hydraulic fluid (oil) contained in the cylinder 2 is exchanged by circulating through a not shown hole of the piston 3, which is brake-passing, as the piston moves in the cylinder 2.

The behaviour of each hydraulic shock absorber 1 of the hydraulic suspension system of the vehicle can be described according to a damping law in which the force exerted by the shock absorber 1 depends on the speed of the axle-free travel of the corresponding wheel. In other words, the faster the piston 3 moves in the cylinder 2 of the shock absorber, the higher the braking of this piston and the greater the force exerted by the shock absorber 1 on the body 6 of said vehicle.

For each wheel of the vehicle, the hydraulic suspension system also comprises a suspension spring 17 fitted around the damper 1 and having its ends respectively resting, by means of a dish 18, on the body 6 of the vehicle and on a dish 19 integral with the cylinder 2 of the damper. The suspension spring 17 is a constant stiffness (raideur) element whose behaviour can be described by the law according to which the force exerted by the spring 17 on the body 6 of the vehicle depends on the compression of the spring and therefore on the amplitude of the axle travel stroke of the corresponding wheel. In other words, the more compressed the suspension spring 17, the greater the force applied to the body 6 of the vehicle. The suspension spring 17 is substantially able to carry the body 6 of the vehicle while allowing the axle travel.

The suspension system also comprises, for each wheel of the vehicle, two attack stops, a mechanical attack stop 7 and a hydraulic attack stop 9, and two decompression stops, a mechanical decompression stop 16 and a hydraulic decompression stop 15.

Each

mechanical stop

7, 16 is similar in stiffness and therefore exerts a force on the body 6 according to the wheel-axle-free travel of the corresponding wheel. As with the suspension spring 17, the forces exerted on the body 6 of the vehicle by the mechanical attack stop 7 and the mechanical decompression stop 16, respectively, are greater due to the greater stroke between the attack axle and the decompression axle of the corresponding wheel.

Each hydraulic attack stop 9 and hydraulic decompression stop 15 is similar to a buffer in itself and therefore exerts a force on the body 6 of the vehicle according to the speed of the inter-axle travel of the corresponding wheel. As with the hydraulic shock absorber 1, the forces exerted on the body 6 of the vehicle by the hydraulic attack stop 9 and the hydraulic decompression stop 15, respectively, are greater due to the greater speed of the inter-axle travel of the corresponding wheel.

Furthermore, the hydraulic attack stop 9 and the hydraulic decompression stop 15 are stops with progressive force that increases according to the stroke by a progressive reduction of the fluid passage along the stroke, which also provides a greater force due to the greater stroke.

Referring to fig. 1A, a mechanical attack stop 7 is integral with one end of the cylinder 2 of the shock absorber and is positioned axially between this end of the cylinder 2 of the shock absorber and the body 6 of said vehicle. Said mechanical attack stop also has a circular cross section so as to be crossed by the rod 14 of the piston 3 of the buffer 1. Therefore, when the piston 3 exceeds a certain attack stroke, the mechanical attack stop 7 is compressed between the end of the cylinder 2 of the shock absorber 1 and the body 6 of the vehicle in question, so as to strongly brake the stroke of the piston 3 in the cylinder 2 of the shock absorber.

Preferably, the mechanical attack stop 7 is made of an elastic material with a very strong stiffness constant, so that the force exerted by the mechanical attack stop 7 on the body 6 of the vehicle increases very rapidly with the attack axle-to-axle travel of the wheel.

The hydraulic attack stop 9 is fitted in the compression chamber 4 of the cylinder 2 of the shock absorber 1. The hydraulic attack stop 9 comprises a piston 11 integral with a lower bottom wall 12 of the cylinder 2 of the shock absorber and a cylinder 10 intended to be moved by the piston 3 of the shock absorber 1 and along the piston 11 of the attack stop 9 when the latter reaches the vicinity of the end of the attack stroke. The cylinder 10 of the hydraulic stop 7 forms a compression chamber 20 filled with hydraulic fluid which can escape this chamber 20 due to leakage around the piston 11 of the hydraulic attack stop 9 when the piston 3 of the shock absorber moves the cylinder 10 of the hydraulic attack stop 9 towards the lower bottom wall 12 of said shock absorber. The piston 3 of the damper 1 reaching near the end of the attack stroke is thus braked very quickly.

Moreover, the hydraulic attack stop 9 comprises a return spring 21 which surrounds the piston 11 of the hydraulic stop 9 and whose ends respectively axially abut against the lower bottom wall 12 of the cylinder 2 of the shock absorber and against the end annular edge along the orifice edge of the cylinder 10 of the hydraulic stop 9. Thus, when the piston 3 of the shock absorber 1 is distanced from the cylinder 10 of the hydraulic stop 9, the return spring 21 enables the cylinder 10 of the hydraulic attack stop 9 to return to the rest position, from which the piston 11 protrudes.

The hydraulic decompression stop 15 is itself a floating piston (piston) surrounding the rod 14 of the shock absorber 1, so that an annular space 23 is maintained between the rod 14 and the inner edge of the floating piston, through which the hydraulic fluid can circulate. The hydraulic decompression stop 15 is positioned in the decompression chamber 5 of the cylinder 2 of the shock absorber and is positioned axially between the upper end wall 8 of the cylinder 2 of the shock absorber, which is crossed by the rod 14 of the shock absorber, and a flange 22 forming a valve, which is integral with the rod 14 of the shock absorber. The mechanical decompression stop 16 is itself a spring with strong stiffness which is positioned in the decompression chamber 5 and whose ends axially bear against the floating piston 15 and against the upper end wall 8 of the cylinder 2 of the shock absorber 1, respectively.

When the piston 3 of the hydraulic shock absorber 1 moves to the vicinity of the end of the decompression stroke, the flange 22 forming a valve moves the floating piston 15 toward the upper end wall 8 of the cylinder 2 of the shock absorber 1. The moving floating piston 15 thus simultaneously compresses the mechanical decompression stop 16. Moreover, the flange 22 forming the valve closes, while in contact with the floating piston 15, the space 23 between the inner edge of the floating piston 15 and the rod 14, which reduces the section that enables the passage of fluid from above to below the floating piston, and consequently increases the resistance of said hydraulic decompression stop to the movement towards the upper end wall 8 of the cylinder 2 of the shock absorber 1. The piston 3 of the hydraulic shock absorber 1 which reaches near the end of the stroke is therefore braked very rapidly by the two decompression stops 15, 16.

Referring to the graph of fig. 1B, the configuration of the attack stoppers 7, 9 and the decompression stoppers 15, 16 according to the stroke of the piston 3 of the shock absorber 1 in the cylinder 2 of the shock absorber 1 will now be described.

The vertical scale represents the stroke (in millimetres) of the piston 3 of the shock absorber in the cylinder 2 of the shock absorber 1 at the moment of the inter-axle travel stroke of the wheels of said vehicle. The horizontal scale is a visual scale representing the force applied by each element of the hydraulic suspension to the wheel position according to the stroke of the piston 3 in the cylinder 2 of the corresponding shock absorber 1. A zero stroke (zero millimetres) corresponds to the position of the piston 3 of the shock absorber 1 in the cylinder when the suspension of the vehicle is subjected only to the forces exerted by the mass of the vehicle and not to other forces. The vehicle is thus at a reference steady state AR.

The negative stroke of the piston 3 of the shock absorber in the cylinder 2 corresponds to the aggressor wheel axle trip stroke of the wheel, that is to say the suspension tends to compress and the body 6 of the vehicle tends to approach the road with respect to the reference steady state AR. Conversely, the positive stroke of the piston 3 of the shock absorber 1 in the cylinder 2 corresponds to the decompression wheel-axle-trip stroke of the wheel, that is to say the suspension tends to decompress and the body 6 of the vehicle tends to move away from the road with respect to the reference steady state AR.

The attack or decompression stroke of the piston 3 of the shock absorber 1 between-15 mm and 15mm, based on the reference steady state AR, is considered to correspond to a weak-energy wheely stroke DLE representing the most common excitation encountered on a good-quality road.

The attack stroke of the piston 3 of the shock absorber 1 between-15 mm and-50 mm based on the reference steady state AR and the decompression stroke of the piston 3 of the shock absorber 1 between 15mm and 50mm based on the reference steady state AR are considered to correspond to the mid-energy wheelstream stroke DME, which represents an excitation that is also common. These stimuli are encountered on roads that are slightly degraded (when the wheels cross small obstacles, such as small speed bumps).

Finally, it is considered that the attack stroke of the piston 3 of the shock absorber 1, based on the reference steady state AR, exceeding-50 mm up to a maximum of-80 mm, and the decompression stroke of the piston 3 of the shock absorber 1, based on the reference steady state AR, greater than 50mm up to a maximum of 110mm, correspond to the wheelplay stroke DHE of greater energy, which represents a less frequent excitation. These excitations are encountered in particular when the wheel passes over large obstacles of the herringbone deceleration strip type or relatively deep potholes.

For greater convenience in the following of the present description, the attack stroke or decompression stroke of the piston 3 of the shock absorber 1 is expressed in absolute value.

Referring to the graph of fig. 1B, once the stroke of the piston 3 of the damper 1 exceeds an attack stroke of about 10mm, the mechanical attack stop 7 is compressed. The mechanical attack stop 7 thus intervenes rapidly to brake the stroke of the piston 3 of the damper 1 from the start of the intermediate-energy wheel-axle-free stroke DME. When the attack stroke of the piston 3 of the shock absorber 1 exceeds 50mm (in other words, for a higher energy wheel axle inter-stream stroke DHE), the piston 3 of the hydraulic shock absorber 1 forces the movement of the cylinder 10 of the hydraulic attack stop 9 along the corresponding piston 11 to rapidly brake the piston 3 of the shock absorber 1 in the corresponding cylinder 2 by adding a velocity-dependent braking force on the braking force of the mechanical stop 7. The body 6 of the vehicle is thus protected from impacts of damageable elements at the end of travel.

Referring again to the graph of fig. 1B, when the decompression stroke of the piston 3 of the shock absorber 1 exceeds a value of about 70mm, the floating piston 15 of the hydraulic decompression stop moves and simultaneously compresses the spring constituting the mechanical decompression stop 16 when the decompression stroke of the piston 3 of the shock absorber 1 exceeds a value of about 70mm, to rapidly brake the piston 3 of the shock absorber 1 in the corresponding cylinder 2 by the combined action of the two decompression stops.

With reference to fig. 2A and 2B, a suspension system according to a first embodiment of the present invention will now be described.

The suspension system comprises, for each wheel of the vehicle, a damper 1b, a suspension spring 17b and, as mentioned above, two decompression stops, a mechanical decompression stop 16 and a hydraulic decompression stop 15.

The hydraulic suspension system according to the invention also comprises, for each wheel of the vehicle, a mechanical attack stop 7b, shorter than the mechanical attack stop 7 of the prior art, and a hydraulic attack stop 9b, the cylinder 10b of which has a movement amplitude (between 40 and 60 mm) along the corresponding piston 11b between the end of the attack stroke and the end of the decompression stroke. This amplitude of movement is greater than that of the cylinder 10 of the prior art hydraulic attack stop 9 (of the order of 30 mm).

Moreover, the structure of the cylinder 10b of the hydraulic attack stop 9b is different, since the cylinder 10b comprises in its wall a plurality of radial through holes 13 which allow the hydraulic fluid to be input or output to the compression chamber 4 of the cylinder 2 of the shock absorber 1b when the piston 11b and the cylinder 10b of the hydraulic attack stop 9b move with respect to each other. Thus, as the cylinder 10b of the hydraulic attack stop 9b moves along the corresponding piston 11b towards the lower bottom wall 12 of the cylinder 2 of the shock absorber 1b, more and more through holes 13 are blocked by the piston 11b of the hydraulic attack stop 9b, which consequently reduces the overall section of said through holes 13, so that the braking force exerted by the hydraulic attack stop 9b on the body 6 of the vehicle is increased for a constant movement speed of the cylinder 10 b.

The arrangement of the mechanical attack stopper 7b and the hydraulic attack stopper 9b according to the stroke of the piston 3 of the shock absorber 1b is also different from the prior art arrangement.

In fact, when the piston 3 of the hydraulic shock absorber 1b exceeds an attack stroke CA1 of between 0 and 20mm (preferably 10mm), it drives the cylinder 10b of the hydraulic attack stop 9b along the corresponding piston 11 b. For weak and medium-energy wheel-axle-free strokes, the total cross section of the larger number of through holes 13 of the cylinder 10b passing through the hydraulic attack stop 9b is large enough to ensure a gentle braking of the piston 3 of the shock absorber 1. For a higher energy wheel axle inter-stream stroke DHE (in which the piston 3 of the shock absorber 1b is close to the end of the attack stroke), the total cross section of the smaller number of through holes 13 of the cylinder 10b passing through the hydraulic attack stop 9b decreases, because more and more of the through holes 13 are blocked by the piston 11b of the hydraulic attack stop 9b as the cylinder 10b moves along the piston 11b of the hydraulic attack stop 9b towards the lower bottom wall 12 of the cylinder 2 of the shock absorber 1 b: this ensures an increasingly stronger braking of the piston 3 of the damper 1b in order to protect the body 6 and the chassis of the vehicle.

Moreover, once the piston 3 of the buffer 1b exceeds an attack travel CA2 of between 40 and 50mm (preferably 50mm), the mechanical attack stop 7b is compressed and participates in reinforcing the braking of the piston 3 of said buffer 1.

It is noted that, upon compression of the suspension system, the discontinuity of the force exerted by said suspension system (i.e. the origin of the discomfort of the vehicle occupant) is strongly reduced by the hydraulic attack stop 9b, whose cylinder 10b has an extended movement amplitude and which acts before the mechanical attack stop 7 b. Moreover, the force exerted by the hydraulic attack stop 9b depends on both the speed and amplitude of movement of the piston 3 of the damper 1b in the cylinder 2, the braking of the piston 3 of said damper being gradually adapted to the amplitude and speed of the stroke of said piston in the cylinder 2, which has a positive effect also on the comfort of the passengers, in particular for the medium-energy wheel axle inter-stroke DME. Finally, the hydraulic attack stop 9b dissipates the energy without accumulating it, which thus avoids any re-propulsion (effect de balance) during the inter-axle travel with weak and medium energy.

The damper 1b also comprises an operating member 30 which modifies the level of force generated by the movement of the piston 3 in the cylinder 2 according to programmed damping rules which act through electrical connections coupled to a computer 32. In fig. 2B, the variable force level of the movement of the piston 3 in the cylinder 2 is indicated by the variable width of the rectangular area representing the force of the damper 1B.

Depending on a certain amount of received information about the vehicle operation (for example the speed of said vehicle or the steering angle of the front wheels indicating a turn), the computer 32 sends a signal (in particular a current of variable intensity) to the command member 30 to modify the fluid passage on each side of the piston 3 of the damper 1b in order to vary in real time the level of force and therefore the oscillation damping of said suspension. Controls operated by the driver may also be provided to select different modes (e.g., comfort mode and sport mode).

The computer 32 may comprise a limited number of buffering laws, in particular only two predefined laws controlled by current or by current absence, which represents a very simple system, or a continuously varying range of buffering levels.

With reference to fig. 4A and 4B, a suspension system according to a second embodiment of the present invention will now be described.

Elements have the same reference numbers on these figures as on fig. 2A and 2B and are therefore not described again here.

The hydraulic suspension system according to the second embodiment of the invention further includes, for each wheel of the vehicle, a mechanical decompression stop 16b that is longer than the mechanical decompression stop 16 of the prior art. The floating piston of the hydraulic decompression stop 15b according to the second embodiment of the invention therefore has a movement amplitude (for example between 40 and 80 mm) around the stem 14 of the shock absorber 1 and between a rest position and a decompression stroke end position. This amplitude of movement is greater than that of the floating piston of the hydraulic decompression stop 15 of the prior art (of the order of 20 to 30 mm). Moreover, the extension of the movement amplitude of the hydraulic decompression stop 15b can reduce the stiffness of the spring of the mechanical decompression stop 16b so as to hardly cause braking of the piston 3 of the shock absorber 1 under decompression.

Furthermore, the floating piston 15b of said hydraulic decompression stop is formed by an annular ring radially grooved over the entire thickness and intended to slide along the rod 14 of the shock absorber 1 in order to maintain an annular space 23b between the rod 14 and the inner edge of the floating piston 15b, while the upper portion of the decompression chamber 5 of the cylinder 2 of the shock absorber 1 comprises a substantially conical wall 2b whose cross section decreases upwards towards the wall 8 of the shock absorber 1. Therefore, the force exerted by the decompression stops 15b, 16b on the body of the vehicle increases very gradually with the travel of the floating piston 15 b: as the floating piston 15b moves along the conical wall 2b towards the upper end wall 8b of the cylinder 2 of the damper 1, the notch of the floating piston 15b and the annular space 23b are gradually closed, which thereby reduces the hydraulic fluid passage section. This therefore ensures a damping that is variable as a function of the stroke of the floating piston 15b, while at the same time significantly improving the control of the vertical movement of the body of the vehicle and thus the comfort of the vehicle.

With reference to fig. 3, for both embodiments of the invention, the horizontal axis shows the speed V (in meters per second) of movement of the piston 3 in the cylinder 2, and the vertical axis shows the force (in daN) on this piston. For variable currents applied in the control member 30, different buffer laws 34 exist for current increments of 0.1A, from a very weak buffer 36 between-75 and +150daN for currents of 0.4A to a higher buffer 38 between-600 and +650daN for currents of 1.6A.

In the event of a loss of current in the control means 30 (for example due to a failure of the computer 32), these control means are arranged to be automatically placed in a state providing a medium damping law 40 which enables the route to be continued with a sufficient compromise between comfort and safety.

Improved suspension comfort is achieved by combining the elements of the hydraulic suspension system of the present invention. In fact, for the less energetic wheel-axle excursion stroke DLE, which does not reach the attack stroke CA1 acting on the hydraulic attack stop 9b, a weak or very weak force level of the buffer 1b is set, in order to obtain a slower and greater amplitude movement of the body 6. Thus, for weak energy wheely travel, a reduction of suspension forces is obtained and a better absorption of minor irregularities of the road is obtained.

Then, for larger irregularities of the road accompanied by a medium-energy attack axle trip travel DME, a gradual increase of the force level of the damper 1b is provided, which adds to the force sent by the hydraulic attack stop 9b and also has a gradual action that varies with the axle trip travel and speed.

Finally, for larger irregularities of the road accompanied by a higher energy aggressive axle trip travel DHE, a larger force level of the damper is set, which is simultaneously added to the forces sent by the hydraulic aggressive stop 9b and the mechanical aggressive stop 7b, respectively.

It is noted that the hydraulic suspension system according to the present invention, which comprises prior art arranged in a new combination, can thus be developed and manufactured at reduced costs by using existing production processes.

The configuration thus described is not limited to the embodiment shown on fig. 2A, 2B, 4A, and 4B described above. The described configuration is given only as a non-limiting example. Various modifications may be added without departing from the scope of the invention. In particular, the present invention is not limited to a single configuration of the hydraulic attack stop 9 b. For example, it is possible to envisage a hydraulic attack stop 9b, the cylinder 10b of which is integral with the inner wall of the compression chamber 4 of the buffer 1b and the piston 11b of which is intended to be moved in the corresponding cylinder 10b by the piston 3 of the buffer 1. Of course, any type of hydraulic attack stop 9b known and able to be housed in the compression chamber 4 of the buffer 1b is contemplated. It is also conceivable that, for each wheel of the vehicle, the suspension spring 17 or the mechanical attack stop 7b is offset outside the hydraulic shock absorber 1b and fitted between the journal bracket of the wheel and the body 6 of said vehicle, in juxtaposition to said hydraulic shock absorber 1 b.

Claims

1. A hydraulic suspension system of an axle of a vehicle, comprising, for each wheel of the axle: a damper (1b) having a cylinder (2) and a piston (3) movable in the cylinder to delimit in the cylinder two chambers (4, 5) of compression and decompression, respectively, interposed between a body (6) of the vehicle and a journal bracket of a wheel of the vehicle; a hydraulic attack stop (9b) with a piston, fitted in the compression chamber (4) and comprising a cylinder (10b) and a piston (11b) movable with respect to each other, characterized in that the hydraulic suspension system further comprises a compressible mechanical attack stop (7b) positioned between the cylinder (2) and the body (6) of the vehicle or between the journal bracket and the body (6) of the vehicle, the piston (11b) and the cylinder (10b) of the hydraulic attack stop (9b) being intended to move with respect to each other during the stroke of the piston (3) of the shock absorber (1b) when the piston of the shock absorber reaches a first attack stroke (CA1) in the cylinder (2) of the shock absorber (1b), the mechanical attack stop (7b) being intended to be greater than the piston (3) of the shock absorber in the cylinder of the shock absorber -a second attack stroke (CA2) of the first attack stroke (CA1) is compressed between the cylinder (2) of the shock absorber and the body (6) of the vehicle or between the journal bracket and the body (6) of the vehicle, and-the hydraulic suspension system comprises a computer (32) acting on an operating member (30) operating the shock absorber (1b) which modifies the level of the force generated by the movement of the piston (3) in the cylinder (2), and-the computer (32) comprises a limited number of laws which predefine the level of the force generated by the movement of the piston (3) in the cylinder (2), and-the operating member (30) of the shock absorber (1b) comprises a function law for automatically placing these in a condition providing an intermediate damping (40) when the signal of the computer (32) is missing, the medium cushioning law is between the weakest force level (36) and the highest force level (38).

2. The hydraulic suspension system according to claim 1, characterized in that the first attack stroke (CA1) of the piston (3) of the shock absorber (1b) is between zero and twenty millimetres based on the reference steady state (AR) of the vehicle.

3. The hydraulic suspension system according to claim 1 or 2, characterized in that the second attack stroke (CA2) of the piston (3) of the shock absorber (1b) is greater than forty millimeters based on the reference steady state (AR) of the vehicle.

4. Hydraulic suspension system according to claim 1, characterized in that the computer (32) comprises a continuously variable range of the level of the force generated by the movement of the piston (3) in the cylinder (2).

5. The hydraulic suspension system according to any one of claims 1, 2 and 4, characterized in that the mechanical attack stop (7b) is made of elastomeric material and has a circular cross section so as to be crossed by a stem (14) of a piston of the shock absorber (1b), said stem being coupled with a bodywork (6) of the vehicle.

6. A hydraulic suspension system according to any one of claims 1, 2 and 4, characterized in that it comprises, for each wheel of the axle, a suspension spring (17) fitted around the damper (1 b).

7. The hydraulic suspension system according to any one of claims 1, 2 and 4, characterized in that it further comprises a hydraulic decompression stop (15b) fitted in the decompression chamber (5) of the cylinder (2) of the corresponding shock absorber (1 b).

8. The hydraulic suspension system according to claim 7, characterized in that the hydraulic decompression stop (15b) is arranged to act when the stroke of the piston (3) of the shock absorber (1b) reaches a decompression stroke (CD) of less than fifty millimetres based on a reference steady state (AR) of the vehicle.

9. The hydraulic suspension system according to claim 7, characterized in that it comprises a mechanical decompression stop (16b) arranged for acting simultaneously with the hydraulic decompression stop (15 b).

10. The hydraulic suspension system according to claim 9, characterized in that the hydraulic decompression stop (15b) comprises a floating piston arranged in the decompression chamber (5), which surrounds the rod (14) of the damper (1b) and comprises a fluid passage (23) between its two sides, the hydraulic decompression stop (15b) further comprising a flange (22) integral with the rod (14), which is arranged on a first side of the floating piston, which is turned towards the piston (3) of the damper (1b) and which forms a valve for closing the fluid passage (23) when the flange rests on the floating piston, the hydraulic decompression stop further comprising a spring arranged on the other side of the floating piston.

11. The hydraulic suspension system of any one of claims 1, 2, 4 and 8 to 10, wherein the vehicle is a motor vehicle.

12. A vehicle comprising a hydraulic suspension system according to any one of claims 1 to 11.

13. The vehicle of claim 12, characterized in that the vehicle is a motor vehicle.