Jounce bumper

1. A jounce bumper made from a copolyester thermoplastic elastomer ( 18 ) for mounting in a vehicle suspension system comprising a shock absorber, the jounce bumper having a central bore ( 20 ) extending along a compression axis (A), said jounce bumper ( 18 ) comprising an elastically compressible bumper portion ( 24 ) having a wall ( 30 ) comprising a plurality of convolutes stacked in a direction of said compression axis (A), each convolute comprising a crest ( 26 ) and a root ( 28 ), characterized in that the convolutes comprise hollow stiffening elements ( 32 ), formed as an integral portion of the wall ( 30 ), and non-overlapping, and in that a cross-section of the jounce bumper perpendicular to the compression axis is non-circular, the non-circular shape resulting from the stiffening elements and configured to provide a variable compression resistance in relation to an axial compression displacement of the jounce bumper,

wherein the root ( 28 ) is formed as an inward convolute and the crest ( 26 ) is formed as an outward convolute in relation to the center longitudinal axis (A) of the jounce bumper ( 18 ), a root radius of curvature (Rr) being larger than a crest radius of curvature (Rc).

2. The jounce bumper according to claim 1 , wherein said plurality of stacked crests and roots are essentially identical and aligned in the axial direction.

3. The jounce bumper according to claim 1 , wherein the stiffening elements ( 32 ) are arranged in the root of said convolutes.

4. The jounce bumper according to claim 1 , wherein the stiffening elements are arranged at a regular distance from each other around the outer circumference of the jounce bumper.

5. The jounce bumper according to claim 1 , wherein the stiffening elements are provided with a maximum radial height (Tr) in the center of the root and a decreasing radial thickness towards the crests.

6. The jounce bumper according to claim 1 , wherein a ratio (Le 0 /Dc) of the jounce bumper effective length (Le 0 ) over the crest outer diameter (Dc) is smaller than 3.

7. The jounce bumper according to claim 1 , wherein the stiffening element comprises a radial outer wall ( 32 a ) having a width (Ws) in the direction of the peripheral circumference (Op) of the jounce bumper, and sidewalls ( 32 b ) extending from the root ( 28 ) to the radial outer wall ( 32 a ).

8. The jounce bumper according to claim 7 , wherein a ratio of the circumferential width of the ribs to the root circumference, defined by:

the number of ribs multiplied by the width of a rib (Ws),

divided by the root diameter (Dr) multiplied by Pi (approx. 3.14);

is in a range of 0.25 to 0.5.

9. The jounce bumper according to claim 7 , wherein the radial outer wall of the stiffening element has a radius of curvature (Rs) that is larger than the radius of curvature (Rr) of the root.

10. The jounce bumper according to claim 1 , wherein the stiffening elements have a maximum width (Ws) in the center of the root, which decreases in a direction towards a first end ( 34 ) and second end ( 36 ).

11. The jounce bumper according to claim 1 , wherein sidewalls of the stiffening elements are angled at a non-zero draft angle (αd) in relation to a radial line (N) extending through the center of the stiffening element.

12. The jounce bumper according to claim 11 , wherein the draft angle (αd) is in the range of 2° to 30°.

13. The jounce bumper according to claim 1 , wherein the pitch (P) between a crest to the nearest adjacent crest is constant along the elastically compressible bumper portion ( 24 ).

14. The jounce bumper according to claim 1 , wherein the pitch (P) between a crest to the adjacent crest is variable along the elastically compressible bumper portion ( 24 ).

15. An automotive suspension system ( 2 ), comprising the jounce bumper according to claim 1 , wherein the jounce bumper is made of a thermoplastic elastomer.

16. The jounce bumper according to claim 8 , wherein the radial outer wall of the stiffening element has a radius of curvature (Rs) that is larger than the radius of curvature (Rr) of the root.

17. The jounce bumper according to claim 1 , which is made by a blow-molding process.