Suspension for wheeled vehicle

1. Suspension for a wheeled vehicle provided with a wheel and a frame, comprising an elastic element functionally combinable between said wheel and said frame, said suspension comprising a hydro-pneumatic spring functionally combined in series with said elastic element so that the equivalent spring modulus (Keq) of said elastic element and said hydro-pneumatic spring is variable as a function of the distance between said frame and said wheel, said hydro-pneumatic spring being shaped and sized to behave also as an energy dissipator in series to said elastic element and to dissipate kinetic energy of between 20 and 40% of the total kinetic energy collected in each cycle by the hydro-pneumatic spring,

wherein said suspension lacks a fluidic damper arranged in parallel with said elastic element between said frame and said wheel and said hydro-pneumatic spring has a preload force greater than that of said elastic element.

2. Suspension according to claim 1 , wherein said hydro-pneumatic spring comprises a first chamber containing a gas, said first chamber being provided with a partition wall which is sliding, or deformable, within said first chamber as a function of the position of said frame relative to said wheel, in order to change the volume, or pressure, of the gas inside said first chamber.

3. Suspension according to claim 2 , wherein said hydro-pneumatic spring comprises a second and a third chamber fluidically communicating with each other and containing an incompressible fluid, said third chamber being provided with a first portion directly or indirectly combined with said elastic element, and a second portion sealingly constrained and movable with respect to said first portion to transfer said incompressible fluid between said second chamber and said third chamber, and vice versa, when the position of said frame relative to said wheel changes, said wall being slidable, or deformable, as a function of the incompressible fluid volume transferred from said second chamber to said third chamber, and vice versa.

4. Suspension according to claim 3 , wherein said first and said second chamber are formed inside a tank and said wall is slidable, or deformable, inside said tank to define said first chamber and said second chamber.

5. Suspension according to claim 3 , wherein said first portion and said second portion of said third chamber are arranged coaxially to said elastic element.

6. Suspension according to claim 5 , wherein said first portion comprises a first hollow sleeve and said second portion comprises a second hollow sleeve shaped to sealingly slide with respect to said first hollow sleeve.

7. Suspension according to claim 3 , wherein said third chamber has a substantially annular shape.

8. Suspension according to claim 3 wherein said hydro-pneumatic spring comprises a duct for fluidically connecting said second chamber with said third chamber to transfer said incompressible fluid between said second chamber and said third chamber, and vice versa.

9. Suspension according to claim 3 , wherein said hydro-pneumatic spring further comprises means for varying the dissipative effects of said hydro-pneumatic spring.

10. Suspension according to claim 9 , wherein said means for varying the dissipative effects of said hydro-pneumatic spring comprises a controlled-heating element that is arranged in said first chamber.

11. Suspension according to claim 9 , wherein said means for varying the dissipative effects comprise one or more additional ducts fluidically combinable with a duct for fluidically connecting said second chamber with said third chamber, or between said second chamber and said third chamber, and vice versa, and one or more switching valves to operate, in a controlled way, the access of said incompressible fluid to said duct and/or to one or more of said one or more additional ducts, in order to modify the pressure drops of the incompressible fluid during the transfer of said incompressible fluid between said second chamber and said third chamber, and vice versa.

12. Method for the functioning of a suspension for a wheeled vehicle provided with a wheel and a frame, comprising an elastic element functionally combinable between said wheel and said frame, said suspension comprising a hydro-pneumatic spring functionally combined in series with said elastic element so that the equivalent spring modulus (Keq) of said elastic element and said hydro-pneumatic spring is variable as a function of the distance between said frame and said wheel, said hydro-pneumatic spring being shaped and sized to behave also as an energy dissipator in series to said elastic element and to dissipate kinetic energy of between 20 and 40% of the total kinetic energy collected in each cycle by the hydro-pneumatic spring, wherein said suspension lacks a fluidic damper arranged in parallel with said elastic element between said frame and said wheel, said method comprising the step of setting a preload force for said hydro-pneumatic spring greater than that of said elastic element.