Rear swinging fork for a motorcycle

1. A rear swinging fork ( 1 ) for a motorcycle frame, comprising:

two longitudinal extending supporting arms ( 2 , 3 ) each supporting arm comprising in a section transverse to the longitudinal direction of the rear swinging fork ( 1 ) three supporting walls ( 6 , 7 , 8 ), the supporting walls being an upper supporting wall ( 6 ), a lower supporting wall ( 7 ), and an inboard supporting wall ( 8 ) connecting the upper ( 6 ) and lower supporting walls ( 7 );

a transverse cross member ( 4 ) connecting the supporting arms ( 2 , 3 );

wherein each of the supporting arms ( 2 , 3 ) has a pivot mount ( 5 ) for pivotal connection of the rear swinging fork ( 1 ) to the motorcycle frame; and

in a region of each of the ends of the supporting arms, opposite the pivot mounts ( 5 ), a wheel mount ( 11 ) for the rear wheel of a motorcycle;

wherein:

the rear swinging fork is die cast as one piece;

portions of the supporting arms between the cross member ( 4 ) and the pivot mounts ( 5 ) are configured open, and a portion of the inboard supporting wall ( 8 ) also extends integrally between the two supporting arms ( 2 , 3 ) along a portion of the cross member ( 4 ) facing the pivot mounts ( 5 ), where it forms a front wall 10 of the cross member ( 4 ), there being no other cross member provided between the pivot mounts ( 5 ); and

the supporting walls form there between a laterally outwardly open longitudinal cavity.

2. The rear swinging fork as set forth in claim 1 , characterized in that the supporting arms are configured to define a C-shape in transverse cross-section.

3. The rear swinging fork as set forth in claim 1 , characterized in that the inboard supporting wall ( 8 ) comprises a saddle roof configuration subtending an internal angle ( 32 ) in the range of from approximately 160 degrees to approximately 180 degrees.

4. The rear swinging fork as set forth in claim 1 , characterized in that a wall thickness of the inboard supporting wall ( 8 ) increases, in the directions toward the upper supporting wall ( 6 ) and toward the lower supporting wall ( 7 ), from an initial wall thickness substantially in the region of the longitudinal center ( 33 ) of the inboard supporting wall ( 8 ).

5. The rear swinging fork as set forth in claim 1 , characterized in that each of the supporting arms ( 2 , 3 ) comprises two transition portions ( 30 , 31 ), between the inboard supporting wall ( 8 ) and each of the upper supporting wall ( 6 ) and the lower supporting wall ( 7 ) respectively, the transition portions having a wall thickness greater than thicknesses of the supporting walls ( 6 , 7 , 8 ) adjoining the transition portions.

6. The rear swinging fork as set forth in claim 5 , characterized in that the respective wall thicknesses of the upper ( 6 ) and lower supporting walls ( 7 ) decrease, from portions of the supporting walls adjoining the transition portions ( 30 , 31 ), in directions away from the inboard supporting wall ( 8 ) and toward outboard portions of the upper ( 6 ) and lower ( 7 ) supporting walls, as viewed in the longitudinal direction of the rear swinging fork ( 1 ).

7. The rear swinging fork as set forth in claim 1 , characterized in that the swinging fork has a longitudinal center plane ( 22 ) and each upper supporting wall ( 6 ) has a first longitudinal stiffening rib ( 28 ) projecting upward from an outboard portion thereof spaced away from the longitudinal center plane, and each lower supporting wall ( 7 ) has a second longitudinal stiffening rib projecting downward from an outboard portion thereof, the stiffening ribs ( 28 , 29 ) extending substantially from the respective pivot mounts ( 5 ) substantially to the wheel mounts ( 11 ).

8. The rear swinging fork as set forth in claim 7 , characterized in that the first and second longitudinal stiffening ribs ( 28 , 29 ) are disposed outside the cavity ( 16 ) at outboard portions of the upper sporting wall ( 6 ) and lower supporting wall ( 7 ), respectively, and wherein each of the stiffening ribs ( 28 , 29 ) comprises along its longitudinal extent a portion of increasing thickness and a portion of diminishing thickness.

9. The rear swinging fork as set forth in claim 1 , characterized in that a portion of each inboard supporting wall ( 8 ) extends between the two supporting arms ( 2 , 3 ) along at least a portion of the cross member ( 4 ) located oppositely away from the pivot mounts ( 5 ), and defines a rear wall of the cross member ( 4 ).

10. The rear swinging fork as set forth in claim 1 , characterized in that each supporting arm ( 2 , 3 ) comprises, in the cavity ( 16 ) between the pivot mounts ( 5 ) and the cross member ( 4 ), at least one first stiffening rib ( 17 ) extending from the upper supporting wall ( 6 ) to the lower supporting wall ( 7 ).

11. The rear swinging fork as set forth in claim 10 further comprising, between the pivot mount ( 5 ) and the cross member ( 4 ) in each supporting arm, at least one second stiffening rib ( 18 ) extending from the upper supporting wall ( 6 ) to the pivot mount ( 5 ).

12. The rear swinging fork as set forth in claim 11 further comprising, in the cavity ( 16 ) of each supporting arm in the region of the cross member ( 4 ), at least one third stiffening rib ( 20 ) extending from the upper supporting wall ( 6 ) to the lower supporting wall ( 7 ).

13. The rear swinging fork as set forth claim 12 further comprising, in each supporting arm between the mount ( 11 ) and the cross member ( 4 ), at least one fourth stiffening rib ( 23 ) extending from the upper ( 6 ) to the lower supporting wall ( 7 ).

14. The rear swinging fork as set forth in claim 13 further comprising, in the cavity of each supporting arm between the cross member ( 4 ) and the wheel mount ( 11 ), at least one fifth stiffening rib ( 24 ) extending from the upper supporting wall ( 6 ) to a tapped cast lug ( 27 ).

15. The rear swinging fork as set forth in claim 14 , characterized in that each of the stiffening ribs ( 17 , 18 , 20 , 23 , 24 ) extends to the inboard supporting wall ( 8 ) respectively and varies in width along its longitudinal extent.

16. The rear swinging fork as set forth in claim 1 further comprising, in the cavity of each supporting arm at the cross member ( 4 ), a criss-cross arrangement of two stiffening ribs ( 20 ) extending from the upper supporting wall ( 6 ) to the lower supporting wall ( 7 ), wherein a criss-cross portion ( 21 ) of the criss-cross arrangement of stiffening ribs extends inboard toward a longitudinal center plane ( 22 ) of the rear swinging fork ( 1 ).

17. The rear swinging fork as set forth in claim 16 , further comprising in the cross member ( 4 ) a cross member wall ( 34 ), oriented in the longitudinal direction of the rear swinging fork ( 1 ) and separating the cavities ( 16 ) of the supporting arms ( 2 , 3 ), wherein the cross member wall ( 34 ) is attached to the criss-cross arrangement of stiffening ribs ( 20 ).

18. The rear swinging fork as set forth in claim 17 , characterized in that the cross member ( 4 ) comprises:

an upper cross member covering wall ( 14 ) connecting the upper supporting wall ( 6 ) of the two supporting arms ( 2 , 3 ); and

a lower cross member covering wall ( 15 ) connecting the lower supporting wall ( 7 ) of the two supporting arms ( 2 , 3 ); and

wherein the cross member wall ( 34 ) is downswept from the upper cross member covering wall ( 14 ) to the lower cross member covering wall ( 15 ).

19. The rear swinging fork as set forth in claim 18 , further comprising, at the lower cross member covering wall ( 15 ), a bifurcated mount ( 13 ) for a spring damper mechanism.

20. The rear swinging fork as set forth in claim 1 , characterized in that the rear swinging fork ( 1 ) comprises an aluminum alloy AlSi 9 MgMn.

21. A rear swinging fork ( 1 ) for a motorcycle frame, comprising:

two longitudinal extending supporting arms ( 2 , 3 ) each having three supporting walls ( 6 , 7 , 8 ); and

a transverse cross member ( 4 ) connecting the supporting arms ( 2 , 3 );

wherein each of the supporting arms ( 2 , 3 ) has a mount ( 5 ) for pivotal connection of the rear swinging fork ( 1 ) on the motorcycle frame; and

in regions of each of the ends of the supporting arms, opposite the mounts ( 5 ), a wheel mount ( 11 ) for the rear wheel of a motorcycle;

wherein the rear swinging fork is die cast as one piece, and portions of the supporting arms between the cross member ( 4 ) and the mounts ( 5 ) are configured open, and the supporting arms ( 2 , 3 ) each features in a section transverse to the longitudinal direction of the rear swinging fork ( 1 ) an upper supporting wall ( 6 ), a lower supporting wall ( 7 ), and an inboard supporting wall ( 8 ) connecting the upper ( 6 ) and lower supporting wall ( 7 ), the supporting walls forming a laterally outwardly open longitudinal cavity there between; and

wherein further a wall thickness of the inboard supporting wall ( 8 ) increases, in the directions toward the upper supporting wall ( 6 ) and toward the lower supporting wall ( 7 ), from an initial wall thickness substantially in the region of the longitudinal center ( 33 ) of the inboard supporting wall ( 8 ).