Steer by wire road vehicle steering system provided with a telescopic support element for the steering wheel

1. A steering system ( 4 ) for a road vehicle ( 1 ); the steering system ( 4 ) comprises:

a steering wheel ( 6 ) provided with an outer ring ( 15 ), which is mounted so as to rotate around a rotation axis ( 13 ) and has no connection to steering wheels ( 2 );

a support element ( 21 ), which, on one side, can be rigidly fixed on the inside of the vehicle ( 1 ) and, on the other side, is connected to the steering wheel ( 6 ) so as to support the steering wheel ( 6 ); and

a position sensor ( 8 ), which is designed to detect the angular position of the outer ring ( 15 ) of the steering wheel ( 6 ) around the rotation axis ( 13 );

wherein the support element ( 21 ) is telescopic so as to vary its axial size along the rotation axis ( 13 ) in order to change the axial position of the steering wheel ( 6 );

wherein the support element ( 21 ) comprises: an outer body ( 22 ), which can be rigidly fixed on the inside of the vehicle ( 1 ) and is internally hollow; an inner body ( 24 ), which is connected to the steering wheel ( 6 ), is partially arranged on the inside of the outer body ( 22 ), and can axially slide relative to the outer body ( 22 ); and an actuator device ( 26 ), which is designed to axially translate the inner body ( 24 ) relative to the outer body ( 22 ); and

wherein the actuator device ( 26 ) is completely arranged on the inside of the outer body ( 22 ).

2. The steering system ( 4 ) according to claim 1 , wherein the outer body ( 22 ) is tubular and has, on the inside, a chamber ( 23 ), which is open on one side, partially houses the inner body ( 24 ) in an axially sliding manner, and houses the actuator device ( 26 ).

3. The steering system ( 4 ) according to claim 1 , wherein the actuator device ( 26 ) is designed to stop the axial translation between the outer body ( 22 ) and the inner body ( 24 ) so as to make sure that, in use, the steering wheel ( 6 ) remains still in a predefined axial position.

4. The steering system ( 4 ) according to claim 1 , wherein the actuator device ( 26 ) is active and comprises a first electric motor, which causes an axial translation movement of the inner body ( 24 ) relative to the outer body ( 22 ).

5. The steering system ( 4 ) according to claim 4 , wherein the actuator device ( 26 ) comprises:

the first electric motor, which is integral to the outer body ( 22 );

a worm screw, which is caused to rotate by the first electric motor; and

an abutment, which is screwed in the worm screw and is integral to the inner body ( 24 ).

6. The steering system ( 4 ) according to claim 1 , wherein the support element ( 21 ) is not aligned with the steering wheel ( 6 ) and is arranged lower than the steering wheel ( 6 ).

7. The steering system ( 4 ) according to claim 1 and comprising a second electric motor ( 16 ), which applies a variable feedback torque to the outer ring ( 15 ) of the steering wheel ( 6 ), is interposed between the support element ( 21 ) and the steering wheel ( 6 ) so as to support the steering wheel ( 6 ), and comprises a stator ( 17 ), which is rigidly connected to the support element ( 21 ), and a rotor ( 18 ), which is rigidly connected at least to the outer ring ( 15 ) of the steering wheel ( 6 ).

8. The steering system ( 4 ) according to claim 1 and comprising a third electric motor ( 10 ), which is mechanically completely independent of and separate from the steering wheel ( 6 ) and is designed to control the steering of the steering wheels ( 2 ) of the vehicle ( 1 ).

9. The steering system ( 4 ) according to claim 8 and comprising a control unit ( 12 ), which is connected to the position sensor ( 8 ) so as to receive the reading of the angular position of the steering wheel ( 6 ) and is designed to control the third electric motor ( 10 ) so as to adjust the steering of the steering wheels ( 2 ) of the vehicle ( 1 ) based on the angular position of the steering wheel ( 6 ).

10. The steering system ( 4 ) according to claim 1 and comprising a mechanical limit stop device ( 30 ), which is coupled to the outer ring ( 15 ) of the steering wheel ( 6 ) and limits, in both directions, the maximum angular width of the rotation of the steering wheel ( 6 ) around the rotation axis ( 13 ), so that the steering wheel ( 6 ) can make, on the whole, a rotation around the rotation axis ( 13 ) that is greater than 360.degree.

11. The steering system ( 4 ) according to claim 10 , wherein:

the limit stop device ( 30 ) comprises a groove ( 31 ), which is wound in a spiral shape around the rotation axis ( 13 ) over more than 360.degree. and has, at the two opposite ends, two abutments ( 32 ), which define respective stop strikers;

the limit stop device ( 30 ) comprises a pin ( 33 ), which is arranged on the inside of the groove ( 31 ) so as to engage and follow the groove ( 31 ) from an abutment ( 32 ) to the opposite abutment ( 32 );

one between the groove ( 31 ) and the pin ( 33 ) is angularly integral to the outer ring ( 15 ) of the steering wheel ( 6 ), whereas the other one between the groove ( 31 ) and the pin ( 33 ) is angularly integral to a part that does not rotate together with the outer ring ( 15 ) of the steering wheel ( 6 ); and

one between the groove ( 31 ) and the pin ( 33 ) can axially slide relative to the outer ring ( 15 ) of the steering wheel ( 6 ).

12. The steering system ( 4 ) according to claim 11 , wherein:

the groove ( 31 ) is angularly integral to the outer ring ( 15 ) of the steering wheel ( 6 ) and can axially slide relative to the outer ring ( 15 ) of the steering wheel ( 6 ); and

the pin ( 33 ) is rigidly connected to a part that does not rotate together with the steering wheel ( 6 ).

13. The steering system ( 4 ) according to claim 12 , wherein the groove ( 31 ) is coupled to the steering wheel ( 6 ) through a splined coupling.

14. The steering system ( 4 ) according to claim 7 , wherein:

the electric motor ( 16 ) comprises a stator ( 17 ), which does not rotate, and a rotor ( 18 ), which can rotate relative to the stator ( 17 ) around the rotation axis ( 13 );

in the electric motor ( 16 ), the rotor ( 18 ) is internal and, therefore, it is radially arranged on the inside of the stator ( 17 );

the rotor ( 18 ) of the electric motor ( 16 ) comprises a shaft ( 19 ), which supports the steering wheel ( 6 ) and is supported by bearings ( 20 ) interposed between the rotor ( 18 ) and the stator ( 17 ); and

the bearings ( 20 ) supporting the rotor ( 18 ) are coupled to the shaft ( 19 ) of the rotor ( 18 ).

15. The steering system ( 4 ) according to claim 7 , wherein:

the electric motor ( 16 ) comprises a stator ( 17 ), which does not rotate, and a rotor ( 18 ), which can rotate relative to the stator ( 17 ) around the rotation axis ( 13 ); and

in the electric motor ( 16 ), the rotor ( 18 ) is external and, therefore, it is radially arranged on the outside of the stator ( 17 ).

16. The steering system ( 4 ) according to claim 15 , wherein the rotor ( 18 ) of the electric motor ( 16 ) is without shaft.

17. The steering system ( 4 ) according to claim 15 , wherein:

the steering wheel ( 6 ) comprises a central hub ( 14 ) which is fixed, i.e. does not rotate around the rotation axis ( 13 ), and the outer ring ( 15 ) which can rotate around the rotation axis ( 13 ); and

the central hub ( 14 ) of the steering wheel ( 6 ) is directly connected to the stator ( 17 ) of the electric motor ( 16 ), whereas the outer ring ( 15 ) of the steering wheel ( 6 ) is directly connected to the rotor ( 18 ) of the electric motor ( 16 ).

18. The steering system ( 4 ) according to claim 15 , wherein:

the stator ( 17 ) of the electric motor ( 16 ) has, at the center, a cable-leading through duct ( 27 ), which is coaxial to the rotation axis ( 13 ); and

a cabling ( 29 ) is provided, which originates from the central hub ( 14 ) of the steering wheel ( 6 ) and is arranged through the cable-leading duct ( 27 ).