Reinforced rotational molded body

Abstract

The present invention relates to a process for manufacturing parts of a vehicle body (01), the process comprising rotationally molding a dense outer layer (11, 21), rotationally molding a dense inner layer (12, 22), and processing the inner layer in order to improve the mechanical properties of the part.

Description

Technical Field

[0001] Corresponding application This application claims the priority of the previous European application No. 23184269.1 filed in the name of SOFTCAR SA on July 7, 2023, and the content of the previous application is incorporated herein in its entirety by reference.

[0002] Technical field The present invention relates to the manufacture of a vehicle body having a small carbon footprint, having a low ecological impact, and preferably including one or more layers of recycled polymers used to reinforce it, and to the means for its manufacture. These means and steps of the method according to the invention include rotational molding the outer layer of parts of the vehicle body, preferably from new materials. The invention also relates to a manufacturing method that enables the improvement of the mechanical properties of the vehicle body, for example, by using materials resulting from the recycling of previous vehicle bodies.

Background Art

[0003] Since 1938, vehicles have been widely made of steel unibodies. The modulus of elasticity of steel is very high, approximately 190 - 220 GPa, and when the unibody is assembled by welding, it has an optimal cross-sectional second moment of area. However, currently, there are several problems.

[0004] The production of steel in blast furnaces formed using coke generates enormous amounts of CO2. The energy required and CO2 emissions are also intense during the processing of crude steel into steel sheets on rollers. The steel sheets are then lubricated to prevent corrosion before being wound onto reels, which are transported by boat, train, and truck. The mass due to the density of the steel requires a considerable amount of energy for transport. Once the reels arrive at the plant, they are stored in a storage area until they are unwound and degreased. The steel then enters the assembly line at the stamping station. A unibody consists of approximately 350 stamped parts, each requiring the manufacture of roughing tools, semi-finishing tools, and finishing tools. Changing styles requires further investment in all of these tools. The assembly line also requires a very large capital investment (billions of Swiss francs). Finally, the footprint is very large. The presses on the assembly line consume enormous amounts of energy and depend on the supply system. Disturbances to power lines have very serious consequences. Steelmaking generates noise, dust, and vibration and involves the use of strong solvents. The punched-out parts are cut from the steel sheet, and on average, 35% of them are discarded. This waste steel sheet is transported to the blast furnace, but because it contains silicon to promote plastic deformation, it cannot be used to manufacture automotive sheet metal. The steel obtained from the press scraps is resmelted and therefore used for lower-grade secondary applications.

[0005] Because the sheet metal has sharp edges and becomes dirty and heavy, the parts are transferred from one press to another by a robot. The steel sheets are then welded together by a robot to produce a unibody. The unibody is then protected from oxidation in an electrophoretic bath. Preferably, four coats of anti-corrosion paint are then applied before the final thermosetting paint (non-recyclable). Once the unibody is manufactured, manual assembly of the unibody is extremely difficult due to the mass and trajectory from the door opening to the interior of the vehicle, so the assembly of heavy interior features such as seats and dashboards requires robot or electric assistance. Ultimately, the energy used in the assembly line is incompatible with the production of environmentally friendly vehicles, and the higher the degree of automation, the greater the CO2 emissions.

[0006] Another fundamental problem is that the density of steel does not allow for the construction of lightweight vehicles that are compatible with electric propulsion. By making the structure lighter, vehicle performance can be improved and energy consumption can be reduced. In the case of electric propulsion, lightness provides additional performance and range. Sheet metal assembly lines are noisy, dirty, dusty, and require a very large amount of energy. The capital investment for the line is very high, and the line occupies a very large area, so work can be done one after another within the line.

[0007] Sheet metal unibodies are approximately 0.8 mm thick, and sheet metal has a major problem: it can be damaged by hail. Furthermore, corrosion remains the biggest problem for steel vehicles.

[0008] Rotational molding is a known technique that was one of the first methods for processing polymers, and is commonly used to manufacture containers (e.g., reservoirs, tanks, bladder for hydrogen storage, etc.), kayaks, and other large articles. These articles are not technical and generally do not need to be very strong, and there is no high tension on the surface. Polyethylene, polypropylene, and polyamides are used, and these have very low moduli compared to steel, with polyethylene having a very low moduli of about 700 MPa, for example.

[0009] In manufacturing the vehicle body, considerable mechanical strength is required, particularly in the A-pillars, seatbelt anchor points, and doors, to protect occupants from side collisions.

[0010] For example, in the case of articles subjected to mechanical loads such as kayaks, a two-layer component is manufactured. In this configuration, the outer layer of the wall (referred to as the "first layer" or "skin") is preferably thin and dense, and the rotationally molded inner layer (referred to as the "second layer") can also be dense or foamed depending on the required mechanical properties.

[0011] The two layers are fused together during a single operation to heat the mold. If the polymers forming the two layers are chemically compatible, entanglement occurs between the two layers, and this aggregation is a crucial factor for the final mechanical strength of the sandwich being manufactured.

[0012] The foaming of the second layer (inner layer) causes the material to expand, increasing the wall thickness, and therefore the second moment of area of ​​the section and the mechanical strength of the part. Although the foam thus produced has a lower density than the dense part, the part produced by the foaming of the second layer has much higher mechanical strength than the part produced by the single layer. [Overview of the project]

[0013] Summary of the Invention and Embodiments One object of the present invention is to improve prior art processes, methods, and products, in particular, to reinforce new products using recycled materials from end-of-life vehicle bodies. The term "upcycling" is used herein to describe such use.

[0014] The present invention makes it possible to overcome all of the aforementioned drawbacks by manufacturing a vehicle body reinforced with recycled materials from a previously manufactured vehicle body structure (referred to as the "previous vehicle body structure"). In some embodiments, the present invention includes four industrial processes for increasing the second moment of area of ​​a vehicle body structure manufactured using recycled materials from the previous vehicle body structure, and thus applies the principle known in the prior art as "upcycling".

[0015] Because all materials are completely contained within the mold, the body structure is molded as a single piece with no manufacturing waste, and the fully dyed and corrosion-resistant finished parts are a shortcut to a circular economy through the incorporation of recycled polymers from previous body structures.

[0016] The present invention preferably incorporates a rotational molding process of an outer layer (referred to as the "first layer") formed from a new, colored material (however, recycled materials may be incorporated) and one or more reinforcing inner layers made from recycled polymers (referred to as the "second layer," "third layer," etc.). For one or more inner layers, the following methods, described as non-limiting embodiments of the present invention, may be used.

[0017] A first upcycling reinforcement method for improving mechanical properties consists of performing integral foaming, in which material from a previous body structure is preferably atomized and introduced as a second layer via a drop box (an insulated container attached to the mold) during the rotation of the mold after the production of the first layer. The step of expanding the second layer is carried out in that section. The foaming reaction is preferably induced by an exothermic agent, such as OSBH or 4,4'-oxybis(benzenesulfonyl hydrazide) (the reaction can also act with an endothermic agent), and integral foaming occurs due to a runaway thermal reaction associated with the heating of the mold. Integral foaming is used for localized reinforcement within the body, for example, for A, B, and C pillars and / or seat belt anchor points, door collision protection, or vehicle seats.

[0018] In this method, the drop box entrance is preferably located near the center of the vehicle, in the center of the roof on the passenger side. This reinforced area provides greater strength and therefore serves as the best upper anchor point for, for example, the passenger seat belt.

[0019] A second upcycling method for improving mechanical properties is as follows: Firstly, the outer layer is manufactured by rotational molding, preferably using new material, such as coloring. The second layer is preferably formed using recycled material from a previous vehicle body structure, which is then atomized and mixed with a leavening agent, which may preferably contain a nucleating agent.

[0020] This material for forming the second layer is delivered via a drop box during the rotation of the mold to form a foamed layer. To obtain a third inner layer that is denser than the foam, the bubbles on the surface of the foamed second layer expand significantly. Still during the heating phase, hot air is injected into the two-layer rotationally molded part at a temperature higher than the polymer's softening or melting temperature. Depending on the location of one or more hot gas injection points, a dense third layer of polymer (called the "skin") can be generated locally or across the entire surface of the foamed second layer.

[0021] More specifically, at the end of the expansion of the foam layer (i.e., the second layer produced), the third layer is formed by sending a flow of hot air into a mold cavity preferably located in the center of the mold in the center of the inner roof. The hot air is preferably circulated through vents, as shown in Figures 1 and 2.

[0022] This temperature increase causes the bubbles on the surface of the second layer to expand. The bubbles burst under the influence of the temperature, and the material falls onto the foam, generating a skin (i.e., the third layer). The expansion is achieved after the programmed expansion phase is complete.

[0023] Therefore, the part has an outer dense layer (first layer) resulting from two-layer rotational molding, an inner dense layer resulting from the injection of high-temperature gas (expansion of bubbles in the outer layer, third layer of the foam), and an intermediate foam layer (intermediate, second layer) resulting from two-layer rotational molding. Thus, the part has the same mass as a two-layer part, but the inner dense layer closes the sandwich and significantly increases its second moment of area. This system makes it possible to improve the local or overall mechanical properties of a part of the same size without increasing the mass of the part.

[0024] A third upcycling reinforcement method involves simultaneously heating particles of different sizes (powder and fine particles) to improve mechanical properties. Firstly, the outer layer is manufactured by rotational molding, preferably using new material, such as coloring. The second layer is formed by upcycling recycled material from a previous vehicle body structure, which is preferably recombined and then finely powdered.

[0025] The second and third layers are manufactured according to two different particle size spectra. The first powder filled with an expanding agent has a fine particle size (e.g., the particles are in the range of 150 μm to 550 μm according to a specific distribution) and is used to manufacture the (foamed) second layer. The second powder has a larger particle size than the first one (e.g., the particles are in the range of 500 μm to 750 μm according to a specific distribution and a narrow particle size spectrum) and is used to manufacture the (dense) third layer.

[0026] The first layer on the outside of the part is preferably manufactured from unused material. The inner second and third layers are preferably sent to the mold simultaneously via a drop box containing a mixture of two particle sizes of recycled material. Since the finest particles melt first, the powder filled with the expanding agent is deposited on the first layer of unused material, forming the second layer. Then, the larger particles adhere to the second layer (which has not yet reacted), forming the third layer. As the temperature continues to rise within the mold, this causes the expansion of the second layer that was previously covered by the third layer. As a result, a three-layer "sandwich" structure is obtained. This reinforcing material is preferably manufactured throughout the part.

[0027] By using an expanding agent with a lower trigger temperature, it is possible to expand the second layer before the third layer is deposited.

[0028] A fourth method for improving mechanical properties is as follows: First, the outer layer is preferably manufactured by rotational molding using a new material, e.g., coloring. The material of the second layer is preferably formed by a material recycled from a previous vehicle body structure, micronized, and re-formulated. During this re-formulation operation, it is possible to incorporate nanometer fillers aimed at improving mechanical strength, such as nanotubes, e.g., graphene, or other equivalent reinforcing materials, into the recycled material. In order to ensure the traceability of the recycled material, a nanometer tracking device can also be introduced to guarantee the origin and quality of the recycled material.

[0029] The first layer on the outside of the part is preferably made from unused materials. The inner second layer is sent into the mold via a hopper containing a recycled powder mixture containing the above-mentioned additive. This reinforcing material can be manufactured locally or throughout the part.

[0030] These four methods enable the improvement of the mechanical properties of the manufactured parts for parts of the same size without increasing the mass of the parts.

[0031] By the above-mentioned methods and processes, a vehicle body structure having the properties required for use as a vehicle body, for example, can be obtained.

[0032] In some embodiments, local reinforcement can be added, particularly in places that must be very strong and / or where the section of the material is restricted, for example, within the A-pillar, the width of which is restricted such that the driver can maintain a good viewing angle and clearly see the sides of the road. The present invention enables the enhancement of rigidity according to one of the above four methods (integral foaming of the section, addition of a third layer by heating the foam, addition of a third layer by adjusting the particle size of the raw material, and / or addition of a nanometer filler to the raw material).

[0033] The anchor point for the passenger seat belt, which is preferably located in the center of the vehicle, also undergoes significant distortion, particularly in the event of a collision. The present invention enables the reinforcement of the entire roof where the anchor point is located. This reinforcement can be manufactured according to one of the above four methods (integral foaming of the section, addition of a third layer by heating the foam, addition of a third layer by adjusting the particle size of the raw material, and / or addition of a nanometer filler to the raw material).

[0034] The same reinforcement method can be applied to rotationally molded doors to withstand side impacts, to front and rear bumpers to withstand front and rear impacts, to rear seat belt anchor points to withstand collision forces, to C-pillars for strength in the event of a vehicle rollover, or to any other area subject to significant deformation.

[0035] Another means of providing localized reinforcement is to manufacture material bonding bosses, also known as "kiss-offs" in the field of rotational molding. If these kiss-offs are generated directly in the outer first layer, shrinkage of the material during cooling will cause sink marks to appear on the outer surface of the first layer, which is not the level of quality required in the automotive industry. To overcome this problem, material bonding is generated with the second and / or third layers, preventing the formation of dips on the outer surface of the part in question. More specifically, the kiss-offs are formed by generating bosses on the rotational molding mold for the object to be formed (e.g., a car body structure or door). During the rotational molding of the (outer) first layer, there is no material bonding. Material bonding is generated during the formation of the (foamed) second and / or third layer, as described above. A fairly strong part is then obtained that meets the collision resistance requirements necessary for manufacturing a motor car body structure.

[0036] These reinforcement kiss-offs are preferably manufactured in the areas of the part that experience the highest mechanical loads, such as the front and rear seat belt anchor points, A-pillars, C-pillars, roof, front and rear bumpers, or any other areas subject to mechanical strain. They allow for protection of occupants in the event of a side, front, or rear impact, or if the vehicle rolls over. On the doors, they can be positioned at the hip point, preferably at the same height as the door pocket, concealed by them, or at the occupant's shoulder height.

[0037] Materials obtained from the crushing of car bodies and body panels have greater economic value when they are treated with additives and atomized according to a defined spectrum. They can then be resold on the market to manufacture other industrial parts, providing users with sufficient incentive to complete the recycling loop.

[0038] In some embodiments, the present invention relates to a process for manufacturing, for example, a vehicle body component, the process comprising rotationally molding a dense outer layer, rotationally molding a dense inner layer, and processing the inner layer in order to improve the mechanical properties of the component.

[0039] In some embodiments, at least one of the layers is partially or completely formed using recycled and particulate materials from previous vehicle bodies.

[0040] In some embodiments, the processing of the inner layer includes foaming at least a dense inner layer in order to obtain a foamed inner layer.

[0041] In some embodiments, the processing involves locally foaming the entire thickness of the part.

[0042] In some embodiments, at least the foamed inner layer is heated to obtain a dense inner layer and a foamed intermediate layer.

[0043] In some embodiments, one or more foamed inner layers are heated by injecting and / or circulating a high-temperature gas, such as air or an equivalent gas, into the interior of the vehicle body.

[0044] In some embodiments, the foamed surface then functions as a guide for the hot gas due to the Coanda effect.

[0045] In some embodiments, drop boxes and / or vents are used to generate high-temperature gas inlets and / or outlets.

[0046] In some embodiments, at least two different particle size spectra are used in the atomization of the previous body, and the atomized material is introduced into the mold via a drop box to produce a foamed second and third layer.

[0047] In some embodiments, the first particle size spectrum is preferably fine, and the second particle size spectrum is larger than the first spectrum.

[0048] In some embodiments, particles of two spectra are sent into a mold, the finest particles melt first to form a second layer on top of the first layer, and then the larger particles adhere to the second layer to form a third layer.

[0049] In some embodiments, the second layer is expanded before the third layer is deposited by using an expander having a low trigger temperature.

[0050] In some embodiments, during the recycling of a previous vehicle body structure, the material is crushed, recombined, and then micronized by incorporating nanometer fillers such as nanotubes or graphene to improve the mechanical properties of the foamed second and third layers.

[0051] In some embodiments, bosses are formed on the dense outer layer during rotational molding, and these bosses (known as kiss-offs) allow the materials to bond together during the processing of the inner layer.

[0052] In some embodiments, the present invention relates to a component manufactured using the manufacturing process described in this application.

[0053] In some embodiments, the component is, for example, a vehicle body structure, or a vehicle body component such as a door or other part.

[0054] In some embodiments, the vehicle body is manufactured in three layers at the seat belt anchor points and / or the A-pillar and / or C-pillar.

[0055] In some embodiments, the component includes at least one material bonding boss.

[0056] In some embodiments, the component is a door, leaf, seat, or hood, and is manufactured from three layers.

[0057] In some embodiments, the present invention relates to a vehicle comprising the parts or body described in this application.

[0058] In some embodiments, the vehicle is equipped with seat belt anchor points located in the center of the roof, on the inside of the vehicle.

[0059] In some embodiments, the present invention relates to a structure forming a vehicle passenger compartment, comprising a body structure and an opening element, wherein the structure is manufactured by rotationally molding the entire body of the vehicle, and each component, such as the body structure and the opening element, is a hollow body comprising at least one dense outer layer and one foamed inner layer and / or foamed intermediate layer manufactured from the same polymer base as the outer layer, with the addition of a foaming agent.

[0060] In some embodiments of the present invention, the structure forming the passenger compartment of a vehicle comprises a body structure manufactured in a mold that includes drop boxes and vents within the wheel arches and roof, wherein the drop boxes include materials intended to form inner and intermediate layers.

[0061] In some embodiments of the present invention, rotationally molded parts of a structure are reinforced by reinforcing members, particularly in areas subject to strain, such as seat belt anchor points, A-pillars, C-pillars, front bumpers, rear bumpers, doors, or hoods, and the reinforcing members are made possible by the proximity of drop boxes in the mold used to form the parts.

[0062] In some embodiments of the present invention, the foamed intermediate layer and / or foamed inner layer and / or dense inner layer of the component are manufactured entirely or partially using recycled materials from previous structural components that form the cabin.

[0063] In some embodiments of the present invention, the reinforcing material can be obtained by locally foaming the entire thickness of the rotationally molded part.

[0064] In some embodiments of the present invention, the reinforcing material can be obtained by heating the foamed inner layer to obtain a dense inner layer and a foamed intermediate layer.

[0065] In some embodiments of the present invention, one or more foamed inner layers are heated by injecting and / or circulating a high-temperature gas, such as air, into the interior of the component.

[0066] In some embodiments of the present invention, the foamed surface functions as a guide for high-temperature gases due to the Coanda effect.

[0067] In some embodiments of the present invention, the structure comprises a vehicle body structure manufactured in a mold in which drop boxes and / or vents are used for both supplying material to the inner layer and for manufacturing inlets and / or outlets for high-temperature gases.

[0068] In some embodiments of the present invention, the structure has one or more components having one or more bridging elements or bonding bosses or kiss-offs that are generated during rotational molding on a dense outer layer, the bridging elements enabling bonding of materials during processing of the inner layer.

[0069] In some embodiments of the present invention, the structure comprises at least one component, wherein the component is manufactured in at least two different particle size spectra to produce foamed second and third layers when one or more prior structural / cabin components are atomized, and is introduced into a mold via one or more drop boxes.

[0070] In some embodiments of the present invention, the first particle size spectrum is fine, and the second particle size spectrum is larger than the first spectrum.

[0071] In some embodiments of the present invention, particles of two spectra are delivered from one or more drop boxes into a mold, the finest particles melt first to form a second layer on top of a first layer, and then larger particles adhere to the second layer to form a third layer.

[0072] In some embodiments of the present invention, the second layer is expanded before the third layer is deposited by using an expander having a low trigger temperature.

[0073] In some embodiments of the present invention, during the recycling of structural components forming a previous cabin, the material is crushed, recombined, and then micronized by incorporating nanometer fillers such as nanotubes or graphene to improve the mechanical properties of the foamed second and / or third layers.

[0074] In some embodiments of the present invention, the structural components forming the passenger compartment are the vehicle body structure, doors, leaves, hood, tailgate, front bumper, or rear bumper.

[0075] In some embodiments of the present invention, the seat belt anchor point is located at the center of the roof, on the inside of the vehicle.

[0076] In some embodiments, the present invention relates to a mold for forming a body structure of a structure forming the passenger compartment of a vehicle described in this application, wherein the mold comprises drop boxes and vents in the wheel arches and roof of the structure, and the drop boxes include a material intended to form an inner layer and an intermediate layer.

[0077] In some embodiments of the present invention, drop boxes and / or vents in the mold are used for both supplying material to the inner layer and creating inlets and / or outlets for high-temperature gases.

[0078] In some embodiments, the present invention relates to a rotationally molded vehicle seat manufactured according to the same process as the process for the structural components forming the passenger compartment described in this application.

[0079] The present invention and its advantages will become more clearly apparent from the following description of embodiments, which are given as non-limiting examples with reference to the accompanying drawings. [Brief explanation of the drawing]

[0080] [Figure 1] This is a bottom view of a rotationally molded vehicle body structure manufactured according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view of a rotationally molded vehicle body structure manufactured according to an embodiment of the present invention. [Figure 3] This is a cross-sectional view of a vehicle wall after rotational molding of two layers according to an embodiment of the present invention, where the inner layer can be made of recycled material from a previous vehicle body (or vehicle body structure). [Figure 4] This is a cross-sectional view of a vehicle wall after the inner layer has been foamed according to an embodiment of the present invention. [Figure 5] This is a cross-sectional view of the vehicle wall after the formation of the inner third layer according to an embodiment of the present invention. [Figure 6] This is a cross-sectional view of a vehicle wall formed by integral foaming according to an embodiment of the present invention. [Figure 7] This figure shows a fastener / seat belt anchor point according to an embodiment of the present invention. [Figure 8] This figure shows a fastener / seat belt anchor point according to an embodiment of the present invention. [Figure 9] This figure shows a fastener / seat belt anchor point according to an embodiment of the present invention. [Figure 10]This figure shows an embodiment of a kiss-off (or material bonding boss) on a component used to reinforce a structure. [Figure 11] This figure shows an embodiment of a kiss-off (or material bonding boss) on a component used to reinforce a structure. [Figure 12] This figure shows an embodiment of a kiss-off (or material bonding boss) on a component used to reinforce a structure. [Figure 13] This figure shows an embodiment of a kiss-off (or material bonding boss) on a component used to reinforce a structure. [Figure 14] This figure shows the complete body of a vehicle, i.e., the structural components that form the vehicle's passenger compartment, such as the body structure, doors, hood, or tailgate. Figure 14 also shows seats that do not form part of the body. [Modes for carrying out the invention]

[0081] Element reference number -01 Vehicle Body Structure -02 Roof -03 Seatbelt anchor point -04 A-pillar -05 C-pillar -06 Wheel Arch -07 Door Sill -08 Windshield sill -09 Bumper -10 Vehicle body wall -11 Dense outer layer -12 Dense Inner Layer -13 Foamed inner layer -14 Dense Inner Layer -15 Foamed intermediate layer -20 Guest room wall -21 Dense outer layer -22 Dense Inner Layer -23 Foamed inner layer -24 Dense Inner Layer -25 Foamed intermediate layer -30 Dropbox -31 Vent -32 Seat belt -33 Bridge element or layer bonding boss or kiss-off -34 Material joint -35 Shape of layer 21 for generating kiss-off -40 Hood -41 Door or leaf -42 Rear bumper -43 Tailgate -44 Seat

[0082] Detailed description of embodiments of the present invention The present invention is not limited to the described embodiments and can be modified by using means equivalent to those described. Therefore, the present invention and the principles behind it relate to both the vehicle body (or a part thereof) and the process for manufacturing the vehicle body or a part thereof.

[0083] Referring to FIG. 1, a vehicle body structure 01 given as a non-limiting example is designed to be rotationally molded. Thus, it has a hollow body defined by a vehicle body wall 10 and a passenger compartment wall 20. It is provided with a polymer material inlet point, such as a drop box 30, and an air outlet point, such as a vent 31. The drop box 30 and the vent 31 are not elements of the vehicle body structure 01 itself but are elements present on a mold for manufacturing the vehicle body structure 01. However, these inlet and outlet points are shown in the drawings and in this specification to correspond to the vocabulary commonly used by those skilled in the art. Preferably, the drop box 30 and the vent 31 are arranged on the roof 02 and the wheel arch 06 of the vehicle body structure 01. However, they can be arranged at any other position within the vehicle body structure 01.

[0084] The vehicle body structure 01 according to the present invention is manufactured in several consecutive steps described below: a step of rotationally molding an outer layer and then manufacturing one or more inner layers according to the method described below.

[0085] The rotational molding step of the outer layer 11: For example, a polymer in the form of powder or pellets is inserted into a rotational molding mold and injected directly into the cavity of an open mold or into a closed mold through the drop box 30. The mold is heated and rotated on two axes so that the polymer becomes paste-like or liquid and covers all of the walls of the mold. This step forms the dense outer layer 11 of the body wall 10 and the dense outer layer 21 of the passenger compartment wall 20. These layers are said to be dense because they contain little to no voids and their physical and mechanical properties correspond to those of the material (e.g., polymer) from which they are formed.

[0086] Rotational molding of the inner layers: A polymer in powder form, made from unused or recycled materials, is inserted into a closed rotational molding mold via the drop box 30, with the addition of a leavening agent, optionally bound to a nucleating agent. The mold is heated and rotated so that the polymer becomes paste-like or liquid and covers the dense outer layers 11 and 21 of the body wall 10 and the passenger compartment wall 20. The temperature at which the mold is heated is controlled to be below the decomposition temperature of the leavening agent. This stage forms the dense inner layer 12 of the body wall 10 and the dense inner layer 22 of the passenger compartment wall 20, as shown in Figure 3. These layers are said to be dense because they contain little to no voids, and their physical and mechanical properties correspond to those of the polymer on which they are formed.

[0087] Step of foaming the inner layers: The temperature at which the mold is heated is increased until it reaches the decomposition temperature range of the foaming agent incorporated into the polymer of the dense inner layers 12 and 22 of the body wall 10 and the passenger compartment wall 20. The foaming agent causes nucleation of bubbles (preferably nitrogen), which then cause the bubbles to expand, expanding in volume, creating voids in the polymer, and increasing the thickness of the inner walls. The dense inner layers 12 and 22 of the body wall 10 and the passenger compartment wall 20 are transformed to form a foamed inner layer 13 of the body wall 10 and a foamed inner layer 23 of the passenger compartment wall 20, as shown in Figure 4. These layers are said to be foamed because they are formed from polymer cells that form gas pockets. They are thicker than when they were dense. Their mechanical and physical properties are inferior to those of when they were dense.

[0088] At this stage, the manufacturing process is the same as that for standard two-layer components.

[0089] Heating the inner layers: High-temperature air (or any other gas) is injected into the portion between the foamed inner layer 31 of the body wall 10 and the foamed inner layer 23 of the passenger compartment wall 20. The air flows between inlet and outlet points within the component. These points can be the drop box 30 and / or the vent 31 and / or other points specifically created for this function. The temperature of the gas is higher than the decomposition temperature of the foaming agent. The temperature is high enough to cause the air in the bubbles located on the surface to expand, and then the bubbles to burst. Fusion then occurs, thus forming a dense skin on the foamed layer. Thus, the foamed inner layer 13 of the body wall 10 is deformed to form a dense inner layer 14 and a foamed intermediate layer 15. Similarly, the foamed inner layer 23 of the passenger compartment wall 20 is deformed to form a dense inner layer 24 and a foamed intermediate layer 25. This is shown in Figure 5.

[0090] This process allows for the production of a three-layer component (a dense outer layer, a foamed intermediate layer, and a dense inner layer) when the component is rotationally molded using only two polymer layers.

[0091] According to one particular embodiment, several parts of the vehicle body structure 01 are foamed until the foamed inner layer 13 and the foamed inner layer 23 meet, as shown in Figure 6. This can be achieved by a particular part design, namely a locally reduced part thickness, which means that the foam meets in the foaming phase. This can be achieved by locally increasing the thickness of the dense inner layer. Thus, there is locally a larger amount of foaming agent and, therefore, a larger foam thickness at the end of the foaming phase. This can be achieved by locally increasing the foaming temperature, for example, outside the mold, which results in a runaway exothermic reaction of sublimation of the foaming agent, leading to a thicker (and therefore less dense) foam within the part.

[0092] Integrating the body wall 10 and the passenger compartment wall 20 can have several advantages. It allows for localized reinforcement of components without using a third layer (for example, in areas where it is difficult to circulate the flow of hot air). It can also create a preferred channel for circulating hot air during the heating of the inner layer. For example, the door sill 07, windshield sill 08, and bumper 09 can be foamed integrally as shown in Figure 6. Hot air is then injected into the drop box 30 located within the wheel arch 06 at the front of the body structure 01, and the hot air outlet is located within the drop box 30 on the roof, so that all the air enters the A-pillar 04, where a third layer is specifically created. The combination of integral foaming of varying thickness in some locations and the creation of a third layer by circulating high-temperature air in other locations makes it possible to particularly reinforce areas of the vehicle body structure 01 that are subjected to the greatest mechanical load, such as the A-pillar 04, C-pillar 05, or seat belt 32 anchor points 03 (see Figures 7-9), without increasing the mass of the vehicle body structure 01.

[0093] The third and fourth methods described above can also be applied to the structures shown in Figures 1 to 9.

[0094] Figure 10 shows an embodiment of a boss 33, called a kiss-off, for joining layers within the door. The base of the boss 33 is formed within layer 21 during its rotational molding. The material bond (indicated by reference numeral 34) is made between two inner layers, one belonging to the body wall 10 and the other to the passenger compartment wall 20. In Figure 10, layers 14 and 24 intersect, but these kiss-offs can be formed in any of the inner layers (12 / 22, 13 / 23, 14 / 24, respectively) in the embodiments of Figures 3 to 5, for the purpose of avoiding doing so with the outer walls (11, 21) in order to avoid sink marks being visible from the outside. Thus, a considerable reinforcing component is obtained that meets the required strength requirements.

[0095] Figures 11 to 13 show embodiments of the kiss-off 33 at different locations on the vehicle body. These embodiments are illustrative and non-limiting, and such kiss-offs can be positioned in other locations.

[0096] Figure 11 shows a perspective cross-sectional view of a door having an outer layer 10, an inner layer 20, a shape 35 of layer 21 for creating a kiss-off during rotational molding, and a layer joining boss 33. The kiss-off 33 creates a connection between the body wall 10 and the passenger compartment wall 20. Thus, the assembly is much less prone to deformation because, to deform one of the two walls, the other must also be deformed simultaneously, since they are connected by a material joint 34. Therefore, in the event of a side collision, the door is much less prone to being pushed in, ensuring the safety of the occupants.

[0097] Figure 12 shows an internal perspective cross-sectional view of a door having an outer layer 10, an inner layer 20, a shape 35 of layer 21 for generating a kiss-off during rotational molding, and layer bonding bosses 33.

[0098] Figure 13 shows a perspective cross-sectional rear view of a vehicle body structure (as shown in Figures 7-9) having an outer layer 10, an inner layer 20, a shape 35 of layer 21 for generating a kiss-off during rotational molding, and layer joining bosses 33. In this example, the kiss-off is located on the roof and allows the structure to be reinforced with seat belt anchor points (see Figures 7-9). The kiss-off 33 creates a connection between the vehicle body wall 10 and the passenger compartment wall 20. Thus, the assembly is much less prone to deformation because, to deform one of the two walls, the other must also be deformed simultaneously, since it is connected by a material joint 34. In the event of a forward impact that throws the occupant forward and thus pulls the seat belt and its anchor points 03, the anchor points will withstand the pulling of the seat belt much better, ensuring improved occupant safety.

[0099] Figure 14 shows examples of body components such as the body structure 10 and opening elements, namely the doors 41 and hood 40. Other components formed according to the present invention include, for example, seats 44, rear bumpers, tailgates 42, and so on, all of which are known in the field of automotive structures.

[0100] Embodiments are described to provide an overall understanding of the principles underlying the structure, function, manufacture, and use of the systems and processes disclosed herein. One or more of these embodiments are shown in the accompanying drawings. The systems and processes specifically described herein and shown in the accompanying drawings are non-limiting embodiments, and the scope of the invention is not defined solely by the claims. Features illustrated or described in relation to one embodiment can be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the invention. Several problems relating to prior art processes and systems are described herein, and the processes and systems described herein may solve one or more of these problems. In addition, although the invention has been described in conjunction with several embodiments, any alternative, modification, equivalent, or variation that falls within the spirit and scope of the invention is also encompassed by this application.

Claims

1. A structure forming the passenger compartment of a vehicle, comprising a body structure (01) and opening elements (40, 41), wherein the structure is manufactured by rotational molding to form the complete body of the vehicle, and each component such as the body structure (01) and the opening elements (40, 41) is a hollow body comprising at least one dense outer layer (11) and one foamed inner layer and / or foamed intermediate layers (13, 15, 23, 25) manufactured from the same polymer base as the outer layer by adding a foaming agent.

2. A vehicle body structure (01) manufactured in a mold having drop boxes (30) and vents (31) within wheel arches (06) and roof (02), wherein the drop boxes (30) include a material intended to form the inner layers (12-14, 22-24) and intermediate layers (15-25), comprising a structure forming the passenger compartment of a vehicle according to claim 1.

3. A structure forming the passenger compartment of a vehicle according to claim 1 or 2, wherein the rotationally molded part is reinforced particularly in areas subject to strain, particularly in the seat belt (32) anchor point (03), A-pillar (04), C-pillar (05), front bumper (09), rear bumper (42), door (41), or hood (40), and the reinforcement is made possible by the proximity of the drop box (30) in the mold used to form the part.

4. A structure forming a vehicle passenger compartment according to any one of claims 1 to 3, wherein the foamed intermediate layer (15, 25) and / or foamed inner layer (13, 23) and / or dense inner layer (12, 14, 22, 24) of the component is manufactured entirely or partially using recycled materials from a previous structural component that formed the passenger compartment of the vehicle.

5. A structure forming a vehicle passenger compartment according to claim 3 or 4, wherein the reinforcing material is obtained by locally foaming the entire thickness of the rotationally molded part.

6. A structure forming a passenger compartment of a vehicle according to any one of claims 3 to 5, wherein the reinforcing material is obtained by heating the foamed inner layer (13, 23) to obtain a dense inner layer (14, 24) and a foamed intermediate layer (15, 25).

7. A structure forming a vehicle passenger compartment according to claim 6, wherein one or more foamed inner layers (13, 23) are heated by injecting and / or circulating a high-temperature gas, such as air, into the interior of the component.

8. A structure forming a vehicle passenger compartment according to claim 7, wherein the foamed surface functions as a guide for the high-temperature gas by the Coanda effect.

9. A structure forming the passenger compartment of a vehicle according to claim 7 or 8, comprising a body structure (01) manufactured in a mold used for both supplying material to the inner layers (12-14, 22-24) and manufacturing the inlet and / or outlet (24, 24) for the hot gas.

10. A structure forming a vehicle passenger compartment according to any one of claims 1 to 9, wherein one or more components have one or more bridging elements or bonding bosses or kiss-offs (33) generated during rotational molding of the dense outer layers (11, 21), the bridging elements enabling bonding of the materials during processing of the inner layers (12-15, 22-25).

11. A structure for forming a vehicle passenger compartment according to any one of claims 1 to 10, wherein the structure comprises at least one component, and when atomizing one or more prior structural components forming the passenger compartment of the vehicle, the component is manufactured in at least two different particle size spectra and introduced into the mold via one or more drop boxes to produce the foamed second layer (13, 15, 23, 25) and third layer (14, 24).

12. A structure forming a vehicle passenger compartment according to claim 11, wherein the first particle size spectrum is fine and the second particle size spectrum is larger than the first spectrum.

13. A structure for forming a vehicle passenger compartment according to claim 11 or 12, wherein the particles of the two spectra are sent from one or more drop boxes to the mold, the finest particles melt first to form a second layer (13, 15, 23, 25) on the first layer (11, 21), and then larger particles adhere to the second layer to form a third layer (14, 24).

14. A structure forming a vehicle passenger compartment according to claim 13, wherein the second layers (13, 15, 23, 25) are expanded before the third layers (14, 24) are deposited by using an expander having a low trigger temperature.

15. A structure for forming a passenger compartment of a vehicle according to any one of claims 1 to 14, wherein, during the recycling of structural components forming the passenger compartment of a previous vehicle, the material is crushed, recombined, and then atomized by incorporating nanometer fillers such as nanotubes or graphene to improve the mechanical properties of the foamed second layer (13, 15, 23, 25) and / or the third layer (14, 24).

16. A structure for forming a passenger compartment of a vehicle according to any one of claims 1 to 15, wherein the structural component forming the passenger compartment of the vehicle is a vehicle body structure (01), a door (41), a leaf (41), a hood (40), a tailgate (43), a front bumper (09), or a rear bumper (42).

17. A structure forming the passenger compartment of a vehicle according to any one of claims 1 to 16, wherein the seat belt (32) anchor point (03) is located at the center of the roof (02) and inside the vehicle.

18. A mold for forming a body structure (01) of a structure forming the passenger compartment of a vehicle according to any one of claims 1 to 17, wherein the mold comprises drop boxes (30) and vents (31) in the wheel arches (06) and roof (02) of the structure, and the drop boxes (30) include the material intended to form the inner layers (12-14, 22-24) and intermediate layers (15, 25).

19. The mold according to claim 18, wherein a drop box (30) and / or vent (31) are used for both supplying material to the inner layers (12-14, 22-24) and for manufacturing the inlet and / or outlet for the high-temperature gas.

20. A rotationally molded vehicle seat manufactured according to the same process as the process for the structural component forming the passenger compartment according to any one of claims 1 to 19.

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