Internal reinforcement element for a plastic container for a motor vehicle

Description

[0001] The invention relates to an internal reinforcement element for a plastic tank for a motor vehicle. It also relates to a plastic tank for a motor vehicle comprising an internal reinforcement element.

[0002] Traditionally, automotive fuel tanks are designed to maintain a certain amount of fuel at a pressure nearly identical to atmospheric pressure. With the advent of hybrid vehicles, also known as HEVs (Hybrid Electric Vehicles), MHEVs (Mild-Hybrid Electric Vehicles), or PHEVs (Plug-in Hybrid Electric Vehicles)—in other words, vehicles comprising an internal combustion engine and one or more electric motors, which can potentially operate for several months without using the internal combustion engine—it is preferable to maintain pressure in the tank to minimize the passage of gasoline vapors through an activated carbon filter, also called a canister. This is achieved by isolating the canister from the tank using a valve such as a Fuel Tank Isolation Valve (FTIV).

[0003] Such plastic fuel tanks therefore undergo dimensional variations during their life. Firstly, from the moment they come out of the mold due to their cooling which is accompanied by a shrinkage of the material, the said plastic tanks being obtained by extrusion-blowing of a parison, but also during their use, due in particular to overpressures or underpressures of their contents, either due to their thermal expansion during their life, or due to the temperature variation caused by the diurnal cycle, or even due to their aging.

[0004] Typically, plastic fuel tanks for motor vehicles, particularly plastic fuel tanks for hybrid vehicles, include an internal reinforcement element in the form of a pillar connecting two opposing internal surfaces of the tank. Such a pillar must withstand various tests, such as long-term aging or a handling drop from a height of 1 meter, without any degradation of the fuel tank's properties. For example, document EP 3878676 A2 discloses a column-shaped reinforcement element connecting the upper and lower walls of a fuel tank. Document WO2012 / 139962 A1, on the other hand, discloses a circular, hourglass-shaped pillar that exhibits excellent resistance to axial stresses due to tensile / compressive phenomena, as well as to aging and strength tests.However, such a pillar is relatively sensitive to stresses caused by bending and / or torsion phenomena.

[0005] The invention aims, in particular, to overcome these drawbacks of the prior art. More specifically, one objective of the invention is to provide an internal reinforcement element for a plastic tank for a motor vehicle that can withstand not only axial stresses due to tensile / compressive phenomena but also bending and torsional phenomena, said internal reinforcement element being easily obtained by injection molding.

[0006] For this purpose, the invention relates to an internal reinforcement element for a plastic tank for a motor vehicle according to claim 1.

[0007] The curved shape of the central portion and its ribbed structure allow for a better distribution of the stresses transmitted to the internal reinforcing element in different directions, as demonstrated by finite element analyses performed by the inventors. It is clear that such an internal reinforcing element resists bending and torsion better than the prior art pillar, characterized by its unidirectional structure.

[0008] Furthermore, the curved shape of the internal reinforcement element allows it to better overcome the constraints related to its positioning within the tank. For example, the concave portion of the internal reinforcement element can be used to surround an accessory intended for use within the tank, so that the volume of this concave portion is not entirely wasted. The prior art pillar does not allow for this type of arrangement.

[0009] Furthermore, simulation tests have shown that if the end surfaces are not oblong, i.e., if they have sharp angles, then stress is concentrated at these angles, creating a zone of weakness in the internal reinforcement element. The inventors found that by replacing these sharp angles with rounded edges, thus forming an oblong shape, stress is better distributed across the entire internal reinforcement element, without the stress being concentrated on these rounded edges. Similar simulation tests have also shown comparable results due to the narrowing of the cross-section in the transition from the central portion to the axial end portions.

[0010] Advantageously, the internal reinforcement element is made entirely of high-density polyethylene (HDPE) or high-density polyethylene reinforced with glass fibers.

[0011] The internal reinforcement element is thus made from an inexpensive material that is easy to inject and weld. High-density polyethylene can be reinforced with glass fibers, for example up to 10% by weight, to further improve the mechanical properties of the internal reinforcement element.

[0012] Advantageously, the end surfaces each include a network of axial protrusions.

[0013] The axial protrusions facilitate the welding of the internal reinforcement element to the tank walls. In particular, they make welding possible without preheating.

[0014] Preferably, the end surfaces each comprise an openwork set of axial ribs surrounding the network of axial protrusions.

[0015] The axial ribs, which are also intended to be welded to the tank walls, improve the weld strength of the internal reinforcement element to the tank walls by allowing air to escape during welding. In other words, the axial ribs prevent air from becoming trapped between the axial end surfaces and the tank walls, which would weaken the connection between the internal reinforcement element and the tank.

[0016] Advantageously, the radial rib network includes straight ribs extending perpendicularly or parallel to the main axis, defining between them housings of general rectangular parallelepiped shape, and cylindrical ribs, defining between them housings of general cylindrical shape.

[0017] The radial rib network thus forms a grid of blind holes in the central portion of the internal reinforcement element, giving it a general waffle-like shape. This network improves the rigidity of the internal reinforcement element. Furthermore, the radial rib network provides the internal reinforcement element with a noise-dampening effect, similar to the acoustic properties of egg cartons.

[0018] Advantageously, the radial ribs form an asymmetrical network.

[0019] The radial rib network is thus given a keying function, also designated by the Japanese terms "poka yoke", meaning respectively "unintentional error" and "prevent", allowing the position and orientation of the internal reinforcement element in the tank to be imposed and thus reducing the scrap rate in the manufacture of plastic tanks for motor vehicles by preventing errors in the assembly of the internal reinforcement element in the tank.

[0020] Advantageously, the internal reinforcement element includes gripping means located on a lateral wall of the central portion.

[0021] The internal reinforcement element is thus equipped with means allowing it to be adapted to different molding techniques, which helps to make the invention simple to implement.

[0022] Advantageously, the end surfaces have a shape corresponding to a homothety of the corona sector with a ratio k less than or equal to 1, in which each of its four angles is replaced by a rounded edge. In other words, the end surfaces have the shape of a corona sector, extending over an angular sector and a radius corresponding respectively to the angular sector and radius of the corona sector of the central portion multiplied by the ratio k less than 1, whose four angles are replaced by rounded edges.

[0023] The end surfaces, in addition to being simple to manufacture, thus have a shape close to that of the cross-section of the central portion. This ensures that the geometric transition between the central portion and the end portions does not have a shape that would concentrate stresses that could weaken the internal reinforcing element.

[0024] According to a particular embodiment of the invention, the sector-shaped crown of the cross-section of the central portion has an infinite radius, and the oblong, curved shape of the end surface of each of the axial end portions also has an infinite radius. In other words, the reinforcing element has a linear rather than a curved shape.

[0025] Although a linear reinforcement element does not offer as many advantages as a curved reinforcement element, a linear reinforcement element does benefit from the aforementioned advantages related to the oblong shape and the narrowing of the section in the transition from the central portion to the axial end portions.

[0026] The invention also provides for a plastic tank for a motor vehicle comprising an internal reinforcement element as defined above. Brève description of the figures

[0027] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which: [ Fig. 1 ] there figure 1 is a perspective view of an internal reinforcement element for a plastic tank according to an embodiment of the invention, [ Fig. 2 ] there figure 2 is a front view of the internal reinforcement element of the figure 1 , [ Fig. 3 ] there figure 3 is a cross-sectional view of the internal reinforcement element of the figure 1 , [ Fig. 4 ] there figure 4 is a top view of the internal reinforcement element of the figure 1 , And [ Fig. 5 ] there figure 5 is a schematic view of a plastic tank for a motor vehicle, according to the invention, comprising the internal reinforcing element of the figure 1 .

[0028] We represented in figure 1 An internal reinforcement element 2 for a plastic tank for a motor vehicle according to an embodiment of the invention. The internal reinforcement element 2 is made in one piece and entirely of a material suitable for welding to the walls of a plastic tank. The reinforcement element 2 is here made entirely of high-density polyethylene (HDPE) or high-density polyethylene reinforced with glass fibers.

[0029] The reinforcing element 2 comprises a central portion 4 having a cross-section in the shape of a crown sector with respect to a principal axis 6 defining an axial direction or orientation of the reinforcing element 2. The principal axis 6 is defined as the axis passing through the center of rotation of the crown sector, perpendicular to the crown sector. It is the axis of rotation of the crown sector. The principal axis 6 therefore extends beyond the crown sector and the internal reinforcing element 2. For clarity in the figures, the principal axis 6 is represented by means of axes extending into or onto the surface of the internal reinforcing element 2, since the principal property of the principal axis 6 according to the invention is its direction and not its position. In other words, the axes bearing the numeral "6" in the figures correspond to axes parallel to the principal axis and allow the axial direction to be identified.As is best represented in the front view of the internal reinforcement element 2 which is the subject of the . figure 2 , the central portion 4 comprises a network of ribs extending radially with respect to the main axis 6, called the radial rib network 8.

[0030] The radial rib network 8 comprises straight ribs 8a extending perpendicularly or parallel to the main axis 6, defining recesses, or blind holes, generally rectangular in shape. The radial rib network 8 also includes cylindrical ribs 8b, which define recesses, or blind holes, generally cylindrical in shape. The straight ribs 8a contribute to the mechanical properties of the internal reinforcement element 2, notably by improving its resistance to bending and torsion. The radial ribs 8b also contribute to strengthening the mechanical properties of the internal reinforcement element 2, but this is not their only function. The radial ribs 8b form an asymmetrical network that provides a keying feature.In other words, the position of the radial ribs 8b allows an operator to correctly position and orient the internal reinforcement element 2 for installation in a tank, ensuring it is not mounted upside down, which would compromise its reinforcing function. Here on the... figure 2 It is observed that the central portion 4 of the internal reinforcement element 2 comprises a radial rib 8b positioned on the equator of the central portion 4 and another radial rib 8b positioned at a distance from the equator. This second radial rib allows the operator to correctly orient the internal reinforcement element 2 within a tank.

[0031] We represented in figure 3 a cross-sectional view of the internal reinforcing element 2 which allows observation of the crown-like sector shape of the central portion 4. To do this, the blind holes defined by the radial rib network 8 are fictitiously filled to obtain a solid surface, as shown by the dashed lines 9 represented on the figure 3 . The right section of the central portion 4, considered in a plane perpendicular to the principal axis 6, has a first area a 1 .

[0032] Back to the figure 2 The internal reinforcement element 2 comprises gripping means 10 located on a lateral wall 12 of the central portion 4. In this embodiment of the invention, the central portion 4 of the reinforcement element 2 comprises two opposing lateral walls 12, each comprising gripping means 10. Each of these gripping means 10 is in the form of a straight handle connected at two points to the corresponding lateral wall 12. The shape of these gripping means 10 can be compared to that of a briefcase handle. The gripping means 10 facilitate the integration of the internal reinforcement element 2 during the manufacture of the plastic tank, particularly when the tank is produced by blow molding using a technique for inserting the internal reinforcement element into the parison.

[0033] The internal reinforcing element 2 comprises two axial end portions 14 situated on either side of the central portion 4, considering the main axis 6. As is better represented on the figure 4 which is a top view of the internal reinforcing element 2, each of the axial end portions 14 has an oblong and curved end surface 16, inscribed in the cross-section of the central portion 4, having a second area a2 less than the first area a1. Here, the end surfaces 16 have a shape corresponding to a homothety of the crown sector of the central portion with a ratio k less than or equal to 1, each of whose four angles is replaced by a rounded edge 18. Preferably, the ratio k is chosen to be greater than 0.5, or greater than 0.8, or even greater than 0.9. According to an equivalent definition, the end surfaces 16 have the shape of a crown sector, extending over an angular sector and a radius corresponding respectively to the angular sector and the radius of the crown sector of the central portion multiplied by the ratio k less than 1, the four angles of which are replaced by rounded edges 18.The end surfaces 16 are intended to be welded to two opposite walls of a plastic tank.

[0034] Each end surface 16 comprises a network of axial protrusions 20 extending parallel to the main axis 6 over a length of between 1 and 2 mm. The axial protrusions 20 are arranged in radial rows and occupy a majority of the area of ​​the end surface 16. Each end surface 16 further comprises a perforated set of axial ribs 22 surrounding the network of axial protrusions 20. This means that the axial ribs 22 define a contour within which all the axial protrusions 20 are inscribed. The axial ribs 22 are perforated, that is to say, spaced apart from each other, so as to allow air to escape when the end surfaces 16 are welded to the walls of a tank.

[0035] Reinforcing element 2 is manufactured using an injection molding process. Thanks to its geometry, and in particular that of the radial rib network 8, the molding can be carried out simply in one operation.

[0036] We represented in figure 5 A plastic tank 24 according to the invention. The tank 24 comprises an internal reinforcing element 2, which is welded to two opposing walls 26 of the tank 24. The welding of the internal reinforcing element 2 to the walls of the tank 26 can be carried out by any suitable technique, during or after the molding of the tank 24. The gripping means 10 can be grasped by a retaining member (not shown) to facilitate the welding of the reinforcing element 2 to the walls of the tank 26.

[0037] The invention is not limited to the embodiments shown and other embodiments will be obvious to a person skilled in the art. List of references

[0038] 2: Internal reinforcement element 4: Central portion 6: Main axis 8: Radial rib network 8a: Straight rib 8b: Cylindrical rib 9: Dashed line 10: Gripping means 12: Side wall 14: Axial end portion 16: End surface 18: Rounded edge 20: Axial protrusion network 22: Axial rib 24: Reservoir 26: Reservoir wall

Claims

1. An internal reinforcement element (2) for a plastic fuel tank for a motor vehicle, formed in one piece and comprising: - a central portion (4) having a cross-section in the shape of an annulus sector, defining a main axis (6) of the reinforcement element (2) and having a first area, the main axis (6) passing through the center of rotation of the annulus sector perpendicular to the annulus sector, the central portion (4) comprising a network of ribs extending radially with respect to the main axis, referred to as a network of radial ribs (8), and - two axial end portions (14) located on both sides of the central portion (4) with respect to the main axis (6), each of the axial end portions (14) having an end surface (16) of oblong and curved shape, characterized in that the end surface (16) of each of the axial end portions (14) is inscribed within the cross-section of the central portion (4), and has a second area smaller than the first area.

2. The reinforcement element (2) according to the preceding claim, made entirely of high-density polyethylene (HDPE) or glass-fiber-reinforced high-density polyethylene.

3. The reinforcement element (2) according to any one of the preceding claims, wherein the end surfaces (16) each comprise a network of axial protrusions (20).

4. The reinforcement element (2) according to the preceding claim, wherein the end surfaces (16) each comprise an openwork set of axial ribs (22) surrounding the network of axial protrusions (20).

5. The reinforcement element (2) according to any one of the preceding claims, wherein the network of radial ribs (8) comprises straight ribs (8a) extending perpendicular or parallel to the main axis (6), defining between them recesses having a generally rectangular parallelepiped shape, and cylindrical ribs (8b), defining between them recesses having a generally cylindrical shape.

6. The reinforcement element (2) according to any one of the preceding claims, wherein the radial ribs (8) form an asymmetric network.

7. The reinforcement element (2) according to any one of the preceding claims, comprising gripping means (10) located on a side wall (12) of the central portion (4).

8. The reinforcement element (2) according to any one of the preceding claims, wherein the end surfaces (16) have a shape corresponding to a homothety of the annulus sector with a ratio k less than or equal to 1, a shape in which each of its four corners is replaced by a rounded edge.

9. A plastic tank for a motor vehicle (24) comprising an internal reinforcement element (2) according to any one of the preceding claims.