Polymeric crash box for a vehicle and bumper structure

1. A polymeric crash box ( 10 ) for a motor vehicle, said polymeric crash box ( 10 ) having a first open frontal extremity ( 12 ) and a second rear extremity ( 14 ), said polymeric crash box ( 10 ) further comprising a substantially alveolar structure ( 20 ) having a plurality of channels ( 30 ) formed in just one piece, said plurality of channels ( 30 ) extending internally to said crash box ( 10 ) starting from said first open frontal extremity ( 12 ) towards said second rear extremity ( 14 ), each channel ( 30 ) of said plurality of channels ( 30 ) further being internally tapered towards said second rear extremity ( 14 ), at least one substantially planar polymeric fixing element ( 52 ) which is made integral to the same polymeric said crash box ( 10 ) in proximity of said first frontal open extremity ( 12 ) and which is further fixable to a crossbeam ( 60 ), wherein said substantially alveolar structure ( 20 ) comprises a second plurality of channels ( 40 ) formed in a single piece with said plurality of channels ( 30 ), said second plurality of channels ( 40 ) extending starting from said second rear extremity ( 14 ) towards said first frontal open end ( 12 ), each channel ( 40 ) of said second plurality of channels ( 40 ) being internally tapered towards said first frontal open extremity ( 12 ).

2. The polymeric crash box ( 10 ) according to claim 1 , characterized in that said at least one substantially planar polymeric fixing element ( 52 ) comprises a plurality of polymeric stiffening means ( 54 ) each of which is substantially a substantially planar polymeric element with a substantially triangular shape which is made integral with an external lateral surface ( 22 ) and with said at least one substantially planar polymeric fixing element ( 52 ) in order to be substantially parallel to a longitudinal direction.

3. The polymeric crash box ( 10 ) according to claim 1 , characterized in that said at least one substantially planar polymeric fixing element ( 52 ) comprises a base surface and a plurality of through holes ( 53 ), which are formed on the base surface, and in that said polymeric crash box ( 10 ) is fixed to said crossbeam ( 60 ).

4. The polymeric crash box ( 10 ) according to claim 1 , characterized in that said at least one substantially planar polymeric fixing element ( 52 ) are at least two substantially planar polymeric fixing elements ( 52 ) which are fixed at said first open frontal extremity ( 12 ) on opposed sites of an external lateral surface ( 22 ) of said alveolar structure ( 20 ).

5. The polymeric crash box ( 10 ) according to claim 1 , characterized in that each channel ( 40 ) of said second plurality of channels ( 40 ) is surrounded only by channels ( 30 ) of said plurality of channels ( 30 ) internally tapered towards said second rear extremity ( 14 ).

6. The polymeric crash box ( 10 ) according to claim 1 , characterized in that each channel ( 40 ) of said second plurality of channels ( 40 ) is surrounded by at least 3 channels ( 30 ) of said plurality of channels ( 30 ) internally tapered towards said second rear extremity.

7. The polymeric crash box ( 10 ) according to claim 1 , characterized in that said plurality of channels ( 30 ) comprises a plurality of walls ( 32 ) each of which is a wall of another channel ( 30 ) of said plurality of channels ( 30 ) internally tapered towards said second rear extremity ( 14 ), and said plurality of channels ( 30 ) further comprises a plurality of second walls ( 34 ) each of which is a wall of a corresponding channel ( 40 ) of said second plurality of channels ( 40 ), and in that each channel ( 40 ) internally tapered towards said first open frontal extremity ( 12 ) comprises only said plurality of second walls ( 34 ).

8. The polymeric crash box ( 10 ) according to claim 7 , characterized in that each second wall ( 34 ) advantageously has a thickness substantially constant along a longitudinal axis ( 95 ), whereas each wall ( 32 ) of said plurality of walls ( 32 ) has an increasing thickness towards said second rear extremity ( 14 ).

9. The polymeric crash box ( 10 ) according to claim 7 , characterized in that each second wall ( 34 ) is substantially inclined with respect to a longitudinal axis ( 98 ) of a corresponding one of said second plurality of channels ( 40 ) with an angle the absolute value of which is comprised between 0° and 5°.

10. The polymeric crash box ( 10 ) according to claim 7 , characterized in that in that each wall ( 32 ) with respect to a longitudinal axis ( 95 ) of a correspondent channel ( 30 ) has a rake the absolute value of which is comprised 0° and 0.2°.

11. The polymeric crash box ( 10 ) according to claim 1 , further comprising fixing means connectable with a frame of said motor vehicle, which are bound or directly integrated with said second rear extremity ( 14 ), said fixing means comprising a plurality of holes ( 19 ) in said second rear extremity ( 14 ) and which provide a reduction of the total weight of said polymeric crash box ( 10 ).

12. The polymeric crash box ( 10 ) according to claim 1 , characterized in that said crash box ( 10 ) is formed in just one piece of a polymeric material with high impact strength, which with a test of the type ISO 180/1A at 23° C. shows a breaking energy of at least 5 KJ/m 2 , which is a polymeric material chosen between a mixture of a polyphenylene ether (PPE) and a polyammide (PA), a blend of a polyphenylene ether (PPE) and a polybutylene terephthalate (PBT), a blend of a polyphenylene ether (PPE) and a polyethylene (PE), a blend of a polyphenylene ether (PPE) and a polypropylene (PP), a blend of a polyphenylene ether (PPE) and a polystyrene (PS), a blend of a polycarbonate (PC) and a polybutylene terephthalate (PBT), a blend of a polycarbonate (PC) and a polyethylene terephthalate (PET), a polypropylene rubber, a polyamide rubber, and/or their derivates.

13. A bumper structure for a vehicle comprising at least two polymeric crash boxes ( 10 ) according to claim 1 , in which a crossbeam ( 60 ) has a substantially Ω-shaped section and a polymeric external bumper housing having an aesthetic function, said polymeric external bumper housing covering said crossbeam ( 60 ) and said at least two polymeric crash boxes ( 10 ).

14. The bumper structure according to claim 13 , further comprising two substantially planar base portions ( 62 ) to which said at least one fixing element ( 52 ) of said polymeric crash box ( 10 ) is fixed, so that said first frontal open extremity ( 12 ) is spaced with respect to a bottom portion ( 64 ) of said crossbeam ( 60 ), wherein an effort to plastically deform said crossbeam ( 60 ) is less than a minimum effort necessary for deformation of said polymeric crash box ( 10 ).

15. The bumper structure according to claim 14 , characterized in that said crossbeam ( 60 ) comprises a plurality of stiffening elements ( 63 ) each of which has two extremities which are made integral with said two base portions ( 62 ) in order to stiffen said crossbeam ( 60 ) by maintaining a reduced weight and permitting an assembling of said at least two polymeric crash boxes ( 10 ) with said crossbeam ( 60 ).

16. A polymeric crash box ( 10 ) for a motor vehicle, said polymeric crash box ( 10 ) having a first open frontal extremity ( 12 ) and a second rear extremity ( 14 ), said polymeric crash box ( 10 ) further comprising a substantially alveolar structure ( 20 ) having a plurality of channels ( 30 ) formed in just one piece, said plurality of channels ( 30 ) extending internally to said crash box ( 10 ) starting from said first open frontal extremity ( 12 ) towards said second rear extremity ( 14 ), each channel ( 30 ) of said plurality of channels ( 30 ) further being internally tapered towards said second rear extremity ( 14 ), at least one substantially planar polymeric fixing element ( 52 ) which is made integral to the same polymeric said crash box ( 10 ) in proximity of said first frontal open extremity ( 12 ) and which is further fixable to a crossbeam ( 60 ), wherein said at least one substantially planar polymeric fixing element ( 52 ) comprises a plurality of polymeric stiffening means ( 54 ) each of which is substantially a substantially planar polymeric element with a substantially triangular shape which is made integral with said external lateral surface ( 22 ) and with said at least one substantially planar polymeric fixing element ( 52 ) in order to be substantially parallel to said longitudinal direction.