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EP-4438350-B1 - HYDROPNEUMATIC SYSTEM PROVIDED WITH HYDROPNEUMATIC CYLINDERS FOR SUSPENSIONS OF VEHICLE WHEEL ASSEMBLIES, AND ACCORDING VEHICLE

EP4438350B1EP 4438350 B1EP4438350 B1EP 4438350B1EP-4438350-B1

Inventors

  • Lippi, Fabrizio
  • FICKERS, Alexander
  • GIORDANO, Gabriele
  • FRONI, Francesco
  • GHIGLIONE, Stefano
  • MARTINI, ALESSANDRO

Dates

Publication Date
20260506
Application Date
20240321

Claims (13)

  1. Hydropneumatic system (51) for suspensions of vehicle wheel assemblies, the system comprising: - at least two hydropneumatic cylinders (1), each of which is configured to be associated with a respective vehicle wheel assembly, each of the at least two hydropneumatic cylinders extends along a first axis (A), and comprises: a) a first and a second body (10,11), which can move axially relative to each other and suitable to be coupled to respective attachment points in the respective vehicle wheel assembly; b) a first piston element (30), coupled in a fluid-tight manner to said second body (11) and floating along said first axis (A) relative to said second body (11); c) a first and a second chamber (14,15), defined respectively by said first and second body (10,11) and axially separated from each other by said first piston element (30); - a hydraulic supply line (52) communicating with the first chambers (14) of said hydropneumatic cylinders (1) and suitable to receive pressurized oil; characterized by further comprising: - a pneumatic supply line (57) communicating with the second chambers (15) of said hydropneumatic cylinders (1) and suitable to receive pressurized air; and - a pressurization device configured to set the pressure in said pneumatic supply line (57) to a value at least equal to the pressure in said hydraulic supply line (52); and wherein said pressurization device comprises a pressurizing cylinder (61), extending along a second axis (B) and having a third and a fourth chamber (64,65) axially separated from each other by a second piston element (63), floating along said second axis (B); said third chamber (64) communicating with said hydraulic supply line (52), and said fourth chamber (65) communicating with said pneumatic supply line (57); said second piston element (63) having a first and a second face (71,72), which axially delimit said third chamber (64) and, respectively, said fourth chamber (65); said first face (71) having an area larger than an area of said second face (72).
  2. The system according to claim 1, wherein in each said hydropneumatic cylinder (1) said second body (11) comprises two shoulders (32,33) axially facing respective faces of said first piston element (30) so as to define respective axial stroke end positions for said first piston element (30).
  3. The system according to claim 1 or 2, wherein said first body (10) comprises a tubular portion (23) that radially defines said first chamber (14).
  4. The system according to claim 3, wherein said second body (11) comprises a stem (25) that engages said tubular portion (23) and is coupled in a fluid tight manner to an inner surface of said tubular portion (23).
  5. The system according to claim 4, wherein said stem (25) is axially hollow and radially defines said second chamber (15); said first piston element (30) being coupled in a fluid tight manner to an inner cylindrical surface (31) of said stem (25).
  6. The system according to any one of the preceding claims, wherein said second chamber (15) has two ports (17,18) separate from each other, for connection to said pneumatic supply line and for discharging possible oil from said second chamber (15).
  7. The system according to anyone of the previous claims, wherein said hydraulic supply line (52) communicates with said third chamber (64) via a first throttling (69).
  8. The system according to anyone of the previous claims, wherein a valve (77) is interposed between said fourth chamber (65) and a pressurized air source (S); said valve (77) being normally closed and being openable to pressurize said fourth chamber (65) and said pneumatic supply line (57) to a predefined pressure value.
  9. The system according to any one of the preceding claims, wherein said pneumatic supply line (57) communicates with the second chambers (15) of said hydropneumatic cylinders (1) via a respective second throttling (59).
  10. The system according to any one of the preceding claims, wherein the second chambers (15) of said hydropneumatic cylinders (1) are connected to a tank (19) via respective further valves (20), which can be opened to discharge oil from said second chambers (15).
  11. The system according to any one of the preceding claims, wherein said hydraulic supply line (52) communicates with the first chambers (14) of said hydropneumatic cylinders (1) via respective parachute valves (55).
  12. Vehicle comprising: - a hydropneumatic system (51), according to any one of the preceding claims, and - a plurality of wheel assemblies comprising respective suspensions (40), each having at least one of said hydropneumatic cylinders (1).
  13. The vehicle according to claim 12, wherein each said wheel assembly comprises at least one wheel (48), which can rotate about a rotation axis (50), and wherein each said suspension (40) comprises a support structure (42) fixed to a vehicle chassis and at least one oscillating arm (44), having a first end that supports said wheel (48), and a second end coupled to said support structure (42) so as to rotate, together with said wheel (48), about a pivot axis (49); the at least one of said hydropneumatic cylinders (1) being arranged between said wheel (48) and said support structure (42).

Description

TECHNICAL FIELD The present invention relates to a hydropneumatic system provided with hydropneumatic cylinders for suspensions of vehicle wheel assemblies, in particular for a trailer, according to the preamble of claim 1, corresponding to document EP3753763. A furtner hydropneumatic suspension system is disclosed in document DE 10 2011 115402 A1. PRIOR ART In the field of transport by means of tired vehicles, it is known to employ trailers towed by a tractor and comprising a chassis, defining a loading floor, and a plurality of wheel assemblies, each of which is connected to the chassis via a relative suspension comprising a hydraulic cylinder. When the loads to be transported have a relatively high mass, the use of trailers with a high number of axles results to be necessary, so as to increase the payload capacity thereof. The main problem of a multi-axle system is the need to be able to distribute the load in a more or less homogeneous manner on each one of the wheel assemblies. This type of problem is normally solved by solutions in which the cylinders of the suspensions are normally divided into groups, or zones, and the cylinders of each group or zone are supplied via a dedicated hydraulic circuit. In other words, the cylinders belonging to each group, or zone, are put into communication with each other, so as to assure the same hydraulic pressure and consequently assure the same load transferred to the ground. Figure 1 schematically illustrates a layout according to this type of known solutions: specifically, a supply line P supplies pressurized oil to a series of hydraulic cylinders, belonging to the suspensions of respective wheel assemblies, numbered from R1 to R4. In the case where the first wheel encounters a difference in height (be it positive or negative), inside its hydraulic cylinder a local increase (decrease) in pressure takes place, such to make oil flow towards (from) the line P and consequently transfer such pressure to the suspensions of the other wheels. In this manner, the load on the wheels is automatically redistributed: in other words, the load tends to remain constant between the various wheel assemblies and, unless there are dynamic effects, tends to adjust to the unevenness of the ground. Normally, a so-called "parachute" valve V is interposed between the cylinder of each wheel assembly and the line P, capable of blocking the flow in both directions in the case where there is a breakage in the flexible pipe that puts the cylinder in communication with the line P. The intervention of this valve thus prevents the lowering of all the suspensions, and the consequent variation of the attitude of the load, and averts possible consequences deriving from this breakage (i.e. averts damage to the wheel assemblies owing to the overloads, due to the loss of redistribution of the load, and/or the overturning of the trailer due to the sudden lowering of a side of the vehicle). This type of valves is capable of activating, so as to inhibite the passage of oil, when the flow coming out of the cylinder of the suspension reaches a predetermined flow rate threshold, which has to be dimensioned on the basis of the size of the cylinder. This solution, the response of which simply derives from the flow rate of the hydraulic flow, is not capable of distinguishing whether the high value of the oil flow rate passing through the parachute valve V is due to an actual loss of oil (upstream or downstream of such valve V), or to a sudden lifting or lowering of the wheel assembly, deriving from the combination between difference in height of the ground and speed of the vehicle. In other words, the more the vehicle speed is increased, the greater the possibility that the parachute valves V will activate, invalidating the redistribution function of the load between the various wheel assemblies (R1-R4). In this situation, in fact, the suspension of the wheel assembly facing the difference in height of the ground becomes stiff, owing to the closing of the corresponding parachute valve V, and consequently the dynamic behaviour of such wheel assembly will then essentially depend on the characteristics (damping, stiffness, etc...) of the tyre in contact with the ground. It follows that the dynamic overloads to which the wheel assembly, as well as the chassis of the trailer, will be subject, will depend on such characteristics, with a response that may be more or less damped. For example, with a tyre inflated with air, the response will be less reactive and more damped; whereas, with a tyre made of solid rubber, the response will be more reactive and less damped. Furthermore, with regard to the tyres inflated with air, also the inflation pressure (typically of 10 bar) affects the dynamic response of the wheel assembly: upon the increasing of the load, it is suitable to increase the inflation pressure of the tyres, but as collateral effect a more prompt and less damped response will be achieved. This dynamic behavi