FR3011521A1 - METHOD FOR MANUFACTURING A SHOCK ABSORBER FOR A MOTOR VEHICLE - Google Patents

Abstract

A method of manufacturing a motor vehicle shock absorber comprising at least the following steps: - obtaining a strip (19) from a distributor system (21), the strip (19) being made of a composite material comprising continuous fibers and a thermoplastic matrix coating the fibers, - heating the strip (19) to obtain a softened strip (23), - winding the softened strip around a support (25) of generally elongate shape in an axial direction ( D) to obtain a wound strip (10) wound on the support around the axial direction, the wound strip having successive turns (11) offset axially, two successive turns being in contact with each other, - welding of each turn of the strip wound to at least one adjacent turn axially to obtain a welded rolled strip, and - withdrawal of the welded rolled strip of the support. Shock absorber, set of a shock absorber and a bumper, and corresponding motor vehicle.

Description

The present invention relates to a method for manufacturing a shock absorber for a motor vehicle comprising at least one bumper and at least one spar between which the shock absorber is intended. to be located.

The invention also relates to a shock absorber for a motor vehicle, the shock absorber being obtainable by the method of the invention. The invention also relates to an assembly of a bumper and such a shock absorber, and a motor vehicle equipped with at least one such shock absorber. Modern motor vehicles are designed to respond appropriately to different types of possible frontal shocks, such as low-speed shocks or "parking shocks", for speeds of 2.5 to 4 km / h (ECE42), medium-speed shocks or "reparability shocks", for a speed of about 16 km / h (Danner) and shocks at high speeds, for a speed of between 56 and 65 km / h. Such properties of the motor vehicle are obtained thanks to the presence of at least one shock absorber, that is to say an element sufficiently resistant to shocks at low speed and sufficiently deformable to avoid the plasticization of the spar medium-speed shocks . Such a shock absorber generally comprises a tube made of thermosetting matrix composite material, for example an epoxy resin. The tube is generally made by pultrusion. If the tube thus obtained is satisfactory from the point of view of its mechanical properties, it has the disadvantage of not being recyclable, in that the composite material of which it is constituted can not be recovered for another use as material, or in any case can not be economically viable. In general, the tube in question is simply burned at the end of its life or crushed in order to be used as a filler. An object of the invention is therefore to provide a method for manufacturing a motor vehicle shock absorber of the type described above, having the stiffness properties required, but which is also easily recyclable as a material, while staying at a competitive cost. For this purpose, the subject of the invention is a method of manufacturing a motor vehicle shock absorber comprising at least one bumper and at least one spar between which the shock absorber is intended to be located, the method comprising at least the following steps: - obtaining a strip from a dispensing system, the strip being made of composite material comprising continuous fibers and a thermoplastic matrix coating the fibers, - heating the strip to obtain a softened strip, winding the softened strip around a support of generally elongated shape in an axial direction to obtain a strip wound on the support around the axial direction, the wound strip having successive turns axially offset, two successive turns being in contact with each other, - welding each turn of the wound strip to at least one adjacent turn axially to obtain a welded wound strip, and removal of the welded rolled strip from the support. According to particular embodiments, the method comprises one or more of the following characteristics, taken individually or in any technically possible combination: the composite material is unidirectional fibers, the composite material comprises a bi-directional fiber fabric, the fibers preferably aligning substantially in two directions perpendicular to each other when the strip is flat, - the support has a generally cylindrical shape with regular polygonal base or circular base, - during the winding of the strip softened around the support, the support is driven in a rotational movement about the axial direction relative to the dispensing system and translation relative to the dispensing system, the dispensing system preferably being fixed relative to a local reference linked to the earth, - the winding of the softened strip around the support is made in a helix, the ba a wound angle formed in the direction of its length a constant angle with the axial direction, - during the winding of the softened strip around the support, the angle formed by the band wound with the axial direction is adapted so that two successive turns are in edge-to-edge contact, the method further comprises a step of winding an additional strip around the support on the wound strip, the additional strip being made of a composite material comprising continuous fibers and a thermoplastic matrix coating the fibers; the winding of the additional strip is made around the axial direction angularly in the opposite direction to that of the wound strip.

The invention also relates to a shock absorber for a motor vehicle comprising at least one bumper and at least one spar between which the shock absorber is intended to be located, the shock absorber comprising a wound strip of composite material comprising continuous fibers and a thermoplastic matrix coating the fibers, the wound strip being wound on itself around an axial direction and having successive turns offset axially, two successive turns being in contact with each other, each turn the wound strip being welded to at least one axially adjacent coil. The invention also relates to an assembly for a motor vehicle, the assembly comprising at least one bumper, and at least one shock absorber as described above or obtained by a method as described above. The invention finally relates to a motor vehicle comprising an assembly as described above, the absorber being located between the bumper and the spar. The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which: FIG. 1 is a schematic view of a set for a motor vehicle according to FIG. 2 is a schematic view of the wound strip shown in FIG. 1, FIG. 3 is a schematic view of a device for implementing a manufacturing method according to the invention, FIG. a section of the support shown in Figure 3, Figure 5 is a cross section of a support constituting a variant of that shown in Figures 3 and 4, Figure 6 is a cross section of a support constituting a variant of those FIG. 7 is a diagrammatic view illustrating a first variant of the method according to the invention, and FIG. 8 is a diagrammatic view illustrating a second variant of the method. according to the invention. As shown very schematically in FIG. 1, a motor vehicle 1 according to the invention comprises a spar 3 extending for example along a longitudinal direction X of the motor vehicle, a bumper 5 located for example at the front of the motor vehicle , and a shock absorber 7 located longitudinally between the bumper and the spar.

The spar 3 is for example a side spar of the motor vehicle 1, the motor vehicle then comprising another spar (not shown) similar to the spar 3 and substantially parallel to the spar 3, and another shock absorber (not shown) similar to the shock absorber 7.

The bumper 5 is for example formed of a transverse extending transversely from one spar to the other. As can be seen in FIG. 1, the shock absorber 7 has an elongated shape in an axial direction D for example substantially parallel to the longitudinal direction X when the shock absorber 7 is in place in the motor vehicle 1 (FIG. ). The shock absorber 7 comprises a beam 8, for example of square section, and a tube 9 received inside the beam 8. According to a variant not shown, the shock absorber 7 extends transversely in the vehicle 1, the beam 8 being located longitudinally between the spar 3 and a skin of the bumper 5. The tube 9 extends axially over a length L (Figure 2) advantageously between 50 and 200 mm. The shock absorber 7 advantageously has a diameter D1 of between 80 and 120 mm. As shown in Figure 2, the tube 9 has for example a generally cylindrical shape in the axial direction D and circular base. The tube 9 comprises a wound strip 10 made of composite material. In the example shown, the tube 9 is in fact constituted by the wound strip 10. The wound strip 10 is wound on itself around the axial direction D, for example in a helix, so as to form successive turns 11 offset axially. The strip 10 comprises continuous fibers 13 and a thermoplastic matrix 14 coating the fibers. The wound strip 10 forms in the direction of its length an angle α with the axial direction D. By "turns" is meant a portion of the wound strip 10 extending substantially 360 ° around the axial direction D, c ' is to say a complete turn.

The wound strip 10 has a width which is a function of the diameter and the angle a. Advantageously, the angle a is constant over the entire length of the wound strip 10. According to a particular embodiment (not shown), the fibers 13 are unidirectional, for example substantially oriented in the direction of the length of the rolled strip 10 .

According to another particular embodiment (FIG. 2), the fibers 13 are bidirectional. For example, a subset of the fibers 13 is substantially oriented in the direction of the length of the coiled strip 10 and another subset of the fibers 13 is substantially oriented in the width direction of the coiled strip 10.

The matrix 14 is for example polypropylene or polyamide. Any two successive turns 11 are in contact with each other, for example edge to edge. Each turn 11 is welded to at least one coil 11 adjacent axially. The turns 11 in the end position in the axial direction D, that is to say the turns 11 forming the ends of the tube 9, are welded to the turn 11 which is adjacent thereto. The turns 11 in the middle position in the axial direction D, that is to say the turns 11 extending between two other turns 11, are welded to each of two turns 11 adjacent thereto. Advantageously, the weld is continuous following the winding.

A first portion 15 of each turn 11 is welded to a second portion 17 of an adjacent turn 11. The first portion 15 and the second portion 17 are for example in edge-to-edge contact with each other. In other words, it is a solder edge to edge. During a possible shock occurring on the bumper 5, the shock absorber 7 is deformed between the bumper 5 and the spar 3. The tube 9, thanks to its stiffness, absorbs some of the energy shock. The rigidity property is a function of the tensioning force of the spar, that is to say the longitudinal compression force from which the spar deforms plastically. The calibration effort is for example between 80 and 150 kN. Thus, the tube 9 is adapted to deform plastically when it undergoes a compressive force, for example along the axis D, greater than the calibration effort of the spar 3. We will now describe a method according to the invention in 3 and 4. The method makes it possible to obtain the tube 9 described above. A strip 19 of identical composition to the wound strip 10 described above is obtained from a distributor system 21.

The strip 19 is heated to obtain a softened strip 23. Then the softened strip 23 is helically wound on a support 25 to obtain the rolled strip 10 as described above. During or after the winding of the softened strip 23, the turns 11 of the wound strip 10 are welded to each other by means of a heating system 27.

Then the band 23 is for example cut off. The wound strip 10 is then disengaged from the support 25, for example by translating it in the axial direction D.

The wound strip 10 is then cut to the length L to obtain the tube 9. Finally, the tube 9 is placed in the beam 8 to obtain the shock absorber 7. The support 25 is for example a cylinder extending according to the axial direction D and has a circular base 29 shown in FIG. 4.

In a variant, the support 25 has a regular polygonal base, for example a hexagonal base 31 (FIG. 5). According to another variant, the support 25 has a 33 square base (FIG. 6). According to a particular embodiment, the vertices 35 of the base are rounded (FIG. 6) in order to avoid the presence of axially extending edges on the support 25.

During the winding, the support 25 is rotated about the axial direction D with respect to a local reference X, Y, Z bound to the earth. The rotational movement of the support 25 is for example at a constant angular velocity w. The support 25 is driven in a translation movement in the axial direction D, for example at a constant speed V. The dispensing system 21 is advantageously fixed in the local coordinate system X, Y, Z. During the winding, the softened band 23 forms in the direction of its length the angle a with the axial direction D. The angle a is advantageously constant in time.

The angle a, the speed V and the angular velocity w are chosen in the example so that the turns 11 are in continuous contact, edge to edge, successively with each other. According to a variant not shown, the support 25 is only rotary and it is the distributor system 21 which is translated with respect to the local coordinate system X, Y, Z.

According to another variant, which can be combined with the previous one, the support 25 is fixed relative to the local coordinate system X, Y, Z and the dispensing system 21 is driven in a rotational movement with respect to the support 25 around the axial direction D. According to a particular embodiment illustrated in Figure 7, the angle a, the speed V and the angular velocity w are adapted so that the turns 11 overlap partially. The turns 11 then define an overlap zone 37 corresponding to the superposition of two successive turns 11 axially. The dispenser system 21 advantageously comprises an assembly 39 adapted to unwind the band 19 and adjust the mechanical tension of the softened strip 23. The dispensing system 21 comprises a cover and a member 41 adapted to heat the strip 19.

The softened strip 23 is at a temperature chosen according to its thickness, the melting temperature of the matrix and the diameter of the tube. The heating system 27 advantageously comprises a point heating element, for example an infrared source, and a mechanical means for applying a pressure. According to a variant (not shown), the heating system 27 comprises a hot knob that presses the wound strip 10 at the junction between the turns 11. According to another variant (not shown), the welding is done with a contribution of material, for example a supply of a material close to, advantageously similar to, the matrix 14. The welding is advantageously carried out during the winding. According to a particular embodiment, the welding is performed after the winding. After the welding of the wound strip 10 and its release from the support 25, the wound strip 10 is for example cut in two planes Pi, P2 substantially perpendicular to the axial direction D. According to a particular embodiment, an intermediate layer (not shown ), for example made of paper, is placed around the support 25 so as to be interposed between the support 25 and the wound strip 10. This facilitates the release of the wound strip 10 of the support 25.

According to another particular embodiment, illustrated in FIG. 8, a tape similar to the strip 23 is wound on the support 25, at least in part on the wound strip 10, to obtain an additional rolled strip 10A. The wound strips 10 and 10A are wound angularly in opposite directions of each other around the axial direction D.

According to a variant not shown, the wound strips 10 and 10A are wound angularly in the same direction around the axial direction D. Thanks to the characteristics described above, the manufacturing method provides a shock absorber 7 for the motor vehicle 1 having stiffness properties required. The raw materials and the process being inexpensive, the shock absorber 7 is itself a competitive cost. In addition, it is possible to separate the tube 9 from the beam 8 and heat the tube 9 to recover the constituents of the composite material of the rolled strip 10, preferably in the form of granules used as a base material. The shock absorber 7 is therefore easily recyclable.

Several variants of the manufacturing process and the shock absorber 7 have been described. Those skilled in the art will understand that these variants are in general technically combinable. The shape of the section of the shock absorber 7 produced is easily modified simply by changing the shape of the support 25, instead of having to modify an extruder output according to the conventional method.

Claims (10)

CLAIMS 1. A method of manufacturing a shock absorber (7) for a motor vehicle (1) comprising at least one bumper (5) and at least one spar (3) between which the shock absorber (7) is intended to be located, the method comprising at least the following steps: - obtaining a strip (19) from a dispensing system (21), the strip (19) being made of composite material comprising continuous fibers (13) and a thermoplastic matrix (14) coating the fibers (13), - heating the strip (19) to obtain a softened strip (23), - winding the softened strip (23) around a support (25) of shape general elongate in an axial direction (D) to obtain a wound strip (10) wound on the support around the axial direction (D), the wound strip (10) having successive turns (11) axially offset, two turns (11). ) being in contact with each other, - welding each turn (11) of the winding tape e (10) to at least one turn (11) axially adjacent to obtain a rolled strip (10) welded, and - removing the wound strip (10) welded to the support (25). 2. A process according to claim 1, wherein the composite material is unidirectional fibers (13). 3. A process according to claim 1, wherein the composite material comprises a bi-directional fiber fabric (13), the fibers (13) preferably aligning substantially in two directions perpendicular to each other when the web ( 19) is flat. 4. A process according to any one of claims 1 to 3, wherein the carrier (25) has a generally cylindrical shape with a regular polygonal base (31; 33) or circular base (29). 5. A process according to any one of claims 1 to 4, wherein during the winding of the softened strip (23) around the support (25), the support (25) is driven by a rotational movement around the axial direction (D) with respect to the distributor system (21) and translation with respect to the dispensing system (21), the dispensing system (21) being preferably fixed with respect to a local reference (X, Y, Z) tied to the earth. 6. A process according to any one of claims 1 to 5, wherein the winding of the softened strip (23) around the support (25) is made in a helix, wound bandage (10) forming in the direction of its length. a constant angle (a) with the axial direction (D). 7. A method according to claim 6, wherein during the winding of the softened strip (23) around the support (25), the angle (a) formed by the wound strip (10) with the axial direction (D). ) is adapted so that two successive turns (11) are in edge-to-edge contact. 8. A method according to any one of claims 1 to 7, further comprising a step of winding an additional strip (10A) around the support (25) on the wound strip (10), the additional strip (10A). ) being made of a composite material comprising continuous fibers (13) and a thermoplastic matrix (14) coating the fibers (13). 9. A process according to claim 8, wherein the winding of the additional strip (10A) is performed around the axial direction (D) angularly in the opposite direction to that of the wound strip (10). 10. Shock absorber (7) for a motor vehicle (1) comprising at least one bumper (5) and at least one spar (3) between which the shock absorber (7) is intended to be located, the shock absorber (7) comprising a wound strip (10) of composite material comprising continuous fibers (13) and a thermoplastic matrix (14) encasing the fibers (13), the wrapped strip (10) being wound on itself around an axial direction (D) and having successive turns (11) axially offset, two successive turns (11) being in contact with each other, each turn (11) of the wound strip (10) being welded at least one axially adjacent turn (11).