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EP-4739481-A1 - REINFORCED ROTOMOLDED BODY

EP4739481A1EP 4739481 A1EP4739481 A1EP 4739481A1EP-4739481-A1

Abstract

The invention relates to a process for manufacturing parts, for example a vehicle body (01), said process involving rotomolding a compact outer layer (11, 21), rotomolding a compact inner layer (12, 22), and treating the inner layer in order to enhance the mechanical properties of the part.

Inventors

  • Heisel, Guillaume
  • LANDWERLIN, Stéphane
  • VIGOUROUX, PHILIPPE
  • PLUQUET, Patrick
  • CROZIER, ETIENNE
  • THULIEZ, JEAN-LUC

Assignees

  • Softcar SA

Dates

Publication Date
20260513
Application Date
20240629

Claims (20)

  1. 1. Structure forming the passenger compartment of a vehicle, comprising a shell (01), and openings (40, 41), said structure being manufactured by rotational molding and forming the complete body of a vehicle, where each part such as the shell (01) and the openings (40, 41) is a hollow body comprising at least one compact outer layer (11) and a foamed inner and/or middle layer (13, 15, 23, 25) manufactured in the same polymer base as the outer layer, with the addition of a foaming agent.
  2. 2. Structure forming the passenger compartment of a vehicle according to the preceding claim, comprising a shell (01) made in a mold comprising dropboxes (30) and vents (31) at the wheel arches (06) and the roof (02), said dropboxes (30) containing the material intended to form the inner (12-14, 22-24) and middle (15-25) layers.
  3. 3. Structure forming the passenger compartment of a vehicle according to one of the preceding claims, the rotomoulded parts being reinforced by reinforcements in the particularly stressed areas, in particular the anchor points (03) of the belt (32), the A pillars (04), the C pillars (05), the front bumper (09), the rear bumper (42), the doors (41) or the hoods (40), the reinforcement being made possible by the proximity of dropboxes (30) in the mold used to form said parts.
  4. 4. Structure forming the passenger compartment of a vehicle according to one of the preceding claims, the foamed middle layers (15, 25) and/or foamed inner layers (13, 23) and/or compact inner layers (12, 14, 22, 24) of the parts being made entirely or partially from materials resulting from the recycling of previous structural parts forming the passenger compartment of a vehicle.
  5. 5. Structure forming the passenger compartment of a vehicle according to one of claims 3 or 4, obtaining said reinforcements consisting of locally foaming the entire thickness of the rotomolded part.
  6. 6. Structure forming the passenger compartment of a vehicle according to one of claims 3 to 5, obtaining said reinforcements consisting in heating the foamed inner layer (13, 23) to obtain a compact inner layer (14, 24) and a foamed middle layer (15, 25).
  7. 7. Structure forming the passenger compartment of a vehicle according to the preceding claim, in which the heating of the foamed inner layer(s) (13, 23) is carried out by the injection and/or circulation of a hot gas, for example air, inside the part.
  8. 8. Structure forming the passenger compartment of a vehicle according to the preceding claim, in which the foamed surface serves as a guide for the hot gas by the Coanda effect.
  9. 9. Structure forming the passenger compartment of a vehicle according to one of claims 7 or 8, comprising a shell (01) produced in a mold in which dropboxes (30) and/or vents (31) are used both to supply material to the internal layers (12-14, 22-24), and to produce the hot gas inlets and/or outlets (24, 24).
  10. 10. Structure forming the passenger compartment of a vehicle according to one of the preceding claims, in which one or more parts have one or more bridging elements or gluing or kiss-off pads (33) produced during rotational molding on the compact outer layer (11, 21), said bridging element (33) allowing gluing of the materials during the treatment of said inner layer (12-15, 22-25).
  11. 11. Structure forming the passenger compartment of a vehicle according to one of the preceding claims, comprising at least one part in which, during the micronization of one or more previous structural parts forming the passenger compartment of a vehicle, the latter is produced with at least two different particle size spectra and introduced into the mold by one or more drop boxes to produce the second foamed layer (13, 15, 23, 25) and a third layer (14, 24).
  12. 12. Structure forming the passenger compartment of a vehicle according to the preceding claim, in which a first granulometric spectrum is fine and a second granulometric spectrum is greater than the first spectrum.
  13. 13. Structure forming the passenger compartment of a vehicle according to claim 11 or 12, in which the particles of the two spectra are sent into the mold from the dropbox(es), the finest particles melting first to form a second layer (13, 15, 23, 25) on the first layer (11, 21), then the larger particles adhering to the second layer to form a third layer (14, 24).
  14. 14. Structure forming the passenger compartment of a vehicle according to the preceding claim, in which the expansion of the second layer (13, 15, 23, 25) is carried out before the deposition of the third layer (14, 24) using expansion agents having a low triggering temperature.
  15. 15. Structure forming the passenger compartment of a vehicle according to one of the preceding claims, in which, upon recycling of structural parts forming the passenger compartment of a previous vehicle, grinding, reformulation and then micronization are carried out in which nanometric fillers such as nano tubes or graphene are integrated, improving the mechanical characteristics of the second foamed layer (13, 15, 23, 25) and/or the third layer (14, 24).
  16. 16. Structure forming the passenger compartment of a vehicle according to one of the preceding claims, said structural parts forming the passenger compartment of a vehicle are a shell (01), a door (41), a leaf (41), a hood (40), a tailgate (43), a front bumper (09) or rear bumper (42).
  17. 17. Structure forming the passenger compartment of a vehicle according to one of the preceding claims, in which anchor points (03) of the seat belts (32) are located in the center of the roof (02), on the interior side of the vehicle.
  18. 18. Mold for forming a shell (01) of the structure forming the passenger compartment of a vehicle according to one of the preceding claims 1 to 17, said mold comprising dropboxes (30) and vents (31) at the wheel arches (06) and the roof (02) of said structure, said dropboxes (30) containing the material intended to form the inner (12-14, 22-24) and middle (15, 25) layers.
  19. 19. Mold according to the preceding claim, in which dropboxes (30) and/or vents (31) are used both to supply material to the inner layers (12-14, 22-24), and to provide the hot gas inlets and/or outlets.
  20. 20. Rotomoulded vehicle seat produced using a process identical to that of the structural parts forming the passenger compartment according to one of the preceding claims.

Description

Reinforced rotomolded body CORRESPONDING REQUEST The present application claims priority from the earlier European application No. 23184269.1 filed on July 7, 2023 in the name of SOFTCAR SA, the content of this earlier application being incorporated by reference in its entirety into the present application. TECHNICAL AREA The present invention relates to the manufacture of a vehicle body with a low CO2 footprint, with a low ecological impact, and favorably comprising one or more layers of recycled polymer for reinforcing it, and the means for manufacturing the latter. These means and the steps of the method according to the invention comprise the rotational molding of the outer layer of the body parts preferably in a new material. The present invention also relates to production methods for improving the mechanical characteristics of the body, for example by using material from the recycling of a previous vehicle body. PRIOR TECHNIQUE Since 1938, vehicles have been universally made with steel chassis shells. The modulus of the steel is very high, generally between 190 and 220 GPa and the hull frame once assembled by welding presents an optimum quadratic moment. Nevertheless, today many problems arise. Formed from coke, the manufacture of steel in a blast furnace generates a huge amount of CO2. During the transformation of raw steel into sheets in the rolling mill, the energy required and the CO2 emissions are also intense. The sheet is then greased against corrosion before being rolled into coils which are transported by ship, train and truck. The mass due to the density of the steel requires a very high energy for transport. Once they arrive at the factory, the coils are stored protected from the elements before being unrolled and degreased. The steel enters the ironwork line, for stamping. The hull frame is made up of approximately 350 stamped parts, each part requiring the production of roughing tooling, semi-finishing tooling and finishing tooling. A change of style requires a new investment in all of these tools. The ironwork line also requires a very significant investment in capex (several billion CHF). Finally, the footprint is very large. The presses on the ironwork line consume a lot of energy and are dependent on the supply network. A micro power outage has very significant consequences. Working with steel generates noise, dust, vibrations, and the use of heavy solvents. The stamped part is cut from the sheet metal, which on average generates 35% waste. This sheet metal waste is transported to the blast furnaces, and cannot be used to produce automotive sheet metal, because it contains silicon to be more easily plastically deformable. The steel from the press waste will be remelted and will therefore be used in degraded secondary applications. The parts are transferred from one press to another by robots because the sheets are sharp, dirty, and heavy. The sheets are then welded together by robots to arrive at the body frame. The body frame is then protected against oxidation in a cataphoretic bath. Preferably, four layers of anti-corrosion protection are then applied, before the final thermosetting paint (non-recyclable). Once the body frame is made, the assembly of the heavy interior functions, such as the seats and the dashboard, requires robots or motorized assistance, the manual assembly of the body frame being very difficult due to the masses and the trajectories from the door openings to the interior of the vehicle. Ultimately, the energy used on the bodywork line is difficult to reconcile with the production of an ecological vehicle and the higher the automation, the more intense the CO2 generation. Another fundamental problem is that the density of steel does not allow the construction of lightweight vehicles consistent with electric propulsion. Lightening the structures improves vehicle performance and allows for reduced energy consumption. In the case of electric motorization, lightness becomes performance and autonomy in addition. The sheet metal ironwork line is noisy, dirty, dusty, and requires a very high amount of energy. important. The capex of a line is very high, occupies a very large floor space to chain operations together in line. Sheet metal chassis are generally 0.8 mm thick and these sheets have the major problem of being damaged by hail. In addition, corrosion remains the most important problem of steel automobiles. We know about rotational molding, which is one of the first polymer transformation processes, generally used to make containers (such as tanks, vats, hydrogen tank bladders, etc.), kayaks, and other large parts. These parts are not very technical, generally do not require significant mechanical resistance and the surfaces are not very tense. Polyethylene, polypropylene or polyamides are used, which have very low moduli compared to steel: for example, polyethylene has a very low modulus of around 700 MPa. To produce a vehicle body, significant mechanical str