Internal reinforcement element for a plastics tank for a motor vehicle

Abstract

An internal reinforcing element (2) for a plastics material tank for a motor vehicle is made as a single-piece component and comprises: a central portion (4) having a cross section in the form of an annular sector, which cross section defines the main axis of the reinforcing element (1) and has a first area, the central portion (4) comprising a network of ribs extending radially relative to the main axis, referred to as radial ribs (8), and two axial end portions (14) situated on either side of the central portion (4) relative to the main axis, each axial end portion having an elliptical and curved end surface (16) inscribed or inscribed in the cross section of the central portion and having a second area smaller than the first area.

Description

Technical Field

[0001] The invention relates to an internal reinforcement element for a tank made of plastic material for a motor vehicle. The invention also relates to a tank made of plastic material for a motor vehicle comprising the internal reinforcement element and to a method for producing a tank made of plastic material for a motor vehicle. Background Art

[0002] Traditionally, the fuel tanks of motor vehicles have been designed to hold the fuel at a pressure nearly equal 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, motor vehicles comprising a heat engine and one or more electric motors that can potentially operate for months without using the heat engine, it has become preferable to maintain the pressure in the fuel tank in order to reduce the escape of gasoline vapors through the activated carbon filter (also known as the canister). This is achieved by isolating the canister from the fuel tank using, for example, a fuel tank isolation valve (FTIV).

[0003] Therefore, such fuel tanks made of plastic material are subject to dimensional changes during their service life. Such plastic tanks are obtained by extrusion blow molding of a parison, first of all after being removed from the mold and undergoing cooling accompanied by material shrinkage; and also during their use, in particular due to overpressure or underpressure of their contents, or due to thermal expansion during their service life, or due to temperature changes caused by the daily cycle, or due to aging.

[0004] Typically, fuel tanks made of plastic material for motor vehicles, and more specifically for hybrid motor vehicles, include internal reinforcement elements in the form of struts that connect two opposing inner surfaces of the tank. These struts must withstand various tests, such as long-term aging or a one-meter drop, without degrading the tank's performance. Therefore, document WO 2012 / 139962 A1 discloses a circular hourglass-shaped strut that is highly resistant to axial stresses caused by tension / compression, aging, and strength testing. However, this strut is relatively sensitive to stresses caused by bending and / or torsion. Summary of the Invention

[0005] The present invention has for its object in particular to overcome these drawbacks of the prior art. More precisely, it has for its object to provide an internal reinforcing element for a tank made of plastic material for a motor vehicle, which internal reinforcing element is not only resistant to axial stresses due to tension / compression phenomena, but is also resistant to bending and torsion phenomena, and which is also easily obtainable by injection molding.

[0006] To this end, the subject of the invention is an internal reinforcing element for a tank made of plastic material for a motor vehicle, made as a single-piece component and comprising:

[0007] a central portion having a cross section in the form of an annular sector (or a straight section) defining the main axis of the reinforcing element and having a first area, said main axis passing through the centre of rotation of the annular sector and being perpendicular thereto, said central portion comprising a network of ribs extending radially with respect to the main axis, said network of ribs being called radial ribs, and

[0008] - two axial end portions, located on either side of the central portion relative to the main axis, each axial end portion having an elliptical and curved end surface, the end surface being inscribed or inscribed in a cross section of the central portion, the end surface having a second area smaller than the first area.

[0009] The curved shape of the central portion and its ribbed structure allow for a better distribution of the stresses transmitted to the internal reinforcement element in different directions, as demonstrated by the finite element analysis performed by the inventors. It is understood that this internal reinforcement element is more resistant to bending and torsion than prior art struts, which are characterized by a structure that can be described as unidirectional.

[0010] Furthermore, the curved shape of the internal reinforcement element allows it to better overcome the constraints (limitations) associated with its positioning in the tank. For example, the concave portion of the internal reinforcement element can be used to surround an accessory in the tank without completely losing its volume. Prior art struts do not allow this type of arrangement to be achieved.

[0011] Furthermore, simulations have confirmed that if the end surface is not elliptical, that is, if it has protruding (convex) corners (angles), stress concentrations are observed at these corners, thereby forming weak areas of the internal reinforcing element. The inventors have discovered that by replacing these protruding corners with rounded edges (radii), thereby forming an elliptical shape, a better distribution of stresses is observed throughout the internal reinforcing element, without stress concentrations at these rounded edges. Such simulations have also made it possible to observe similar results due to the narrowing of the cross section in the transition (extension) from the central portion to the axial end portions.

[0012] Advantageously, the internal reinforcing element is entirely made of high-density polyethylene (PEHD) or high-density polyethylene reinforced with glass fibres.

[0013] The internal reinforcement element is thus made of a cheap material that is easy to inject and weld.The high density polyethylene may be reinforced with glass fibres, for example up to 10 wt. %, in order to further improve the mechanical properties of the internal reinforcement element.

[0014] Advantageously, the end surfaces each comprise a network of axial projections.

[0015] The axial projections make it possible to facilitate welding of the internal reinforcing element to the wall of the tank. In particular, they make it possible to perform welding without preheating.

[0016] Preferably, the end surfaces each comprise a set of open (perforated, provided with apertures) axial ribs arranged around the network of axial protrusions.

[0017] The axial ribs, which are also used for welding to the tank wall, improve the strength of the weld of the internal reinforcing element to the tank wall by allowing air to escape during welding. In other words, the axial ribs prevent air from being trapped between the axial end surface and the tank wall, which would weaken the connection between the internal reinforcing element and the tank.

[0018] Advantageously, the radial rib network comprises straight ribs extending perpendicularly or parallel to the main axis, the straight ribs defining between them a substantially rectangular hexahedral housing, and cylindrical ribs defining between them a substantially cylindrical housing.

[0019] Thus, the radial rib network forms a network of blind holes in the center of the internal reinforcement element, giving it a roughly waffle-like shape. This network improves the rigidity of the internal reinforcement element. Furthermore, the radial rib network imparts a noise-reducing effect to the internal reinforcement element, similar to the acoustic properties of an egg crate.

[0020] Advantageously, the radial ribs form an asymmetrical web.

[0021] The radial ribs thus have a poka-yoke function, also expressed by the Japanese term "poka yoke", meaning "unintentional error" and "prevention", respectively, which makes it possible to impart a position and orientation to the internal reinforcing element in the tank and thus reduce the scrap rate in the manufacture of tanks made of plastic material for motor vehicles by preventing errors in the installation of the internal reinforcing element in the tank.

[0022] Advantageously, the internal reinforcing element comprises clamping means on the side walls of the central portion.

[0023] Thus, the internal reinforcing element is provided with means enabling it to be adapted to different moulding techniques, which contributes to the ease with which the invention can be implemented.

[0024] Advantageously, the end surface has a shape corresponding to the homonym of an annular sector, with a ratio k less than or equal to 1, in which each of its four corners is replaced by a rounded edge. In other words, the end surface has the shape of an annular sector and extends over an angular sector and a radius corresponding respectively to the angular sector and the radius of the annular sector of the central portion, with the four corners replaced by rounded edges, multiplied by a ratio k less than 1.

[0025] The end surfaces, besides being easy to manufacture, 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 leads to stress concentrations that could weaken the internal reinforcing elements.

[0026] According to a particular embodiment of the invention, the annular sector shape of the cross section of the central portion has an infinite radius, and the elliptical and curved shape of the end surface of each axial end also has an infinite radius. In other words, the reinforcing element has a linear shape rather than a curved shape.

[0027] Although linearly shaped reinforcing elements do not offer as many advantages as curved shaped reinforcing elements, they still benefit from the above-mentioned advantages associated with the elliptical shape and the narrowing of the cross section in the transition from the central portion to the axial ends.

[0028] According to the invention, there is also provided a tank made of plastic material for a motor vehicle, the tank comprising an internal reinforcing element as described above.

[0029] According to the invention, there is also provided a method for producing a tank made of plastic material for a motor vehicle, in which an internal reinforcement element as described above is welded to two opposing inner walls of the tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention will be better understood on reading the following description which is given by way of example only and with reference to the accompanying drawings, in which:

[0031] Figure 1 is a perspective view of an internal reinforcing element for a tank made of plastic material according to one embodiment of the present invention,

[0032] - Figure 2 yes Figure 1 Front view of the internal reinforcement element,

[0033] - Figure 3 yes Figure 1 Cross-sectional view of the internal reinforcement element,

[0034] - Figure 4 yes Figure 1 A top view of the internal reinforcement element, and

[0035] - Figure 5 is a schematic diagram of a tank made of plastic material for a motor vehicle according to the present invention, the tank comprising Figure 1 Internal reinforcement components. DETAILED DESCRIPTION

[0036] Figure 1 1 shows an internal reinforcement element 2 for a tank made of plastic material for a motor vehicle according to one embodiment of the present invention. The internal reinforcement element 2 is made as a single component and is made entirely of a material suitable for welding to the wall of the tank made of plastic material. In this case, the reinforcement element 2 is made entirely of high-density polyethylene (HDPE) or high-density polyethylene reinforced with glass fibers.

[0037] The reinforcing element 2 comprises a central portion 4 having a cross section (straight section) in the shape of an annular sector (crown sector) relative to a main axis 6 which defines the axial direction or orientation of the reinforcing element 2. The main axis 6 is defined as passing through the center of rotation of the annular sector and is perpendicular to the annular sector. This is the axis of rotation of the annular sector. The main axis 6 therefore extends outside the annular sector and the inner reinforcing element 2. For clarity of the drawings, the main axis 6 is shown by an axis extending in the inner reinforcing element 2 or on the surface of the inner reinforcing element 2, since the main property of the main axis 6 according to the invention is its direction and not its position. In other words, the axis with the reference numeral "6" in the drawings corresponds to an axis parallel to the main axis and makes it possible to identify the axial direction. As Figure 2 As better shown in the front view of the subject internal reinforcing element 2 , the central portion 4 comprises a network of ribs extending radially with respect to the main axis 6 , this network of ribs being called radial ribs 8 .

[0038] The network of radial ribs 8 includes straight ribs 8a extending perpendicularly or parallel to the main axis 6 and defining between them generally rectangular parallelepiped-shaped housings or blind holes. The network of radial ribs 8 also includes cylindrical ribs 8b defining between them generally cylindrical housings or blind holes. The straight ribs 8a help improve the mechanical properties of the internal reinforcement element 2, particularly by improving its bending and torsion resistance. The radial ribs 8b also help enhance the mechanical properties of the internal reinforcement element 2, but this is not their only function. The radial ribs 8b form an asymmetric network that allows for error correction. In other words, the positioning of the radial ribs 8b allows the operator to correctly position and orient the internal reinforcement element 2 for installation in the tank, preventing it from being installed in reverse, which might prevent it from optimally performing its reinforcing function. In this example, the central portion 4 of the internal reinforcement element 2 includes a radial rib 8b located at the equator of the central portion 4 and another radial rib 8b located at a distance from the equator. This second radial rib allows the operator to correctly orient the internal reinforcing element 2 in the tank.

[0039] Figure 3 A cross-sectional view (cutaway view) of the internal reinforcing element 2 is shown, which allows observing the shape of the annular sector of the central portion 4. For this purpose, the blind holes defined by the network of radial ribs 8 are imaginarily filled to obtain a solid surface, as in Figure 3 9. The cross section of the central portion 4 considered in a plane perpendicular to the main axis 6 has a first area a1.

[0040] Back to Figure 2 , the internal reinforcing element 2 comprises a clamping device 10 located on a side wall 12 of the central portion 4. In this embodiment of the invention, the central portion 4 of the reinforcing element 2 comprises two opposing side walls 12, each of which comprises a clamping device 10. Each of these clamping devices 10 is in the form of a straight handle connected at two points on the corresponding side wall 12. The shape of these clamping devices 10 can be compared to that of a briefcase handle. The clamping devices 10 can facilitate the integration of the internal reinforcing element 2 during the manufacture of a tank made of plastic material, in particular when the tank is manufactured by blow molding using a technique in which the internal reinforcing element is inserted into a parison.

[0041] The inner reinforcing element 2 comprises two axial ends 14 located on either side of the central portion 4 relative to the main axis 6. Figure 4 As better shown in Figure 4The top view of the internal reinforcement element 2 shows that each axial end 14 has an elliptical (or rectangular) curved end surface 16 inscribed in the cross section of the central portion 4, with a second area a2 smaller than the first area a1. Here, the end surface 16 has a shape corresponding to the homothetic (similarity) of the annular sector of the central portion, with a ratio k less than or equal to 1, with each of the four corners replaced by a rounded edge 18. Preferably, the ratio k is selected to be greater than 0.5, or greater than 0.8, or even greater than 0.9. By equivalent definition, the end surface 16 has the shape of an annular sector, extending over an angular sector and a radius corresponding to the angular sector and radius of the annular sector of the central portion, respectively, multiplied by a ratio k less than 1, with the four corners replaced by rounded edges 18. The end surface 16 is intended to be welded to two opposing walls of the plastic tank.

[0042] Each end surface 16 includes a network of axial projections 20 extending parallel to the main axis 6 over a length between 1 and 2 mm. The axial projections 20 are arranged in radial rows and occupy a majority of the area of ​​the end surface 16. Each end surface 16 also includes a set of perforated axial ribs 22 surrounding the network of axial projections 20. This means that the axial ribs 22 define a profile in which all the axial projections 20 are inscribed. The axial ribs 22 are perforated, in other words, they are spaced apart from one another to allow air to escape when the end surface 16 is welded to the tank wall.

[0043] The reinforcing element 2 is manufactured by an injection molding method. Due to its geometry, in particular the geometry of the network of radial ribs 8, the molding can be done simply in one operation.

[0044] Figure 5 1 shows a tank 24 made of plastic material according to the invention. The tank 24 comprises an internal reinforcing element 2 welded to two opposing walls 26 of the tank 24. The internal reinforcing element 2 can be welded to the walls of the tank 26 by any suitable technique during or after molding of the tank 24. The clamping device 10 can be clamped by a retaining member (not shown) to facilitate welding the reinforcing element 2 to the walls 26 of the tank.

[0045] The present invention is not limited to the embodiments described, and other embodiments will be apparent to those skilled in the art.

[0046] List of Reference Numerals

[0047] 2: Internal reinforcement components

[0048] 4: Center

[0049] 6: Main axis

[0050] 8: Radial ribs

[0051] 8a: Straight Rib

[0052] 8b: Cylindrical rib

[0053] 9: Dashed line

[0054] 10: Clamping device

[0055] 12: Sidewall

[0056] 14: Axial end

[0057] 16: End surface

[0058] 18: Rounded edges

[0059] 20: Axial protrusion

[0060] 22: Axial rib

[0061] 24: Storage tank

[0062] 26: Tank wall

Claims

1. An internal reinforcement element (2) for a tank made of plastic material for a motor vehicle, said internal reinforcement element (2) being made as a single-piece component and comprising: a central portion (4) having a cross section in the form of an annular sector defining the main axis (6) of the internal reinforcing element (2) and having a first area (a1), said main axis (6) passing through the centre of rotation of said annular sector and being perpendicular thereto, said central portion (4) comprising a network of ribs extending radially with respect to said main axis, this network being called a network of radial ribs (8), and - two axial end portions (14) located on either side of the central portion (4) relative to the main axis (6), each axial end portion (14) having an elliptical and curved end surface (16) inscribed or inscribed in a cross section of the central portion (4) and having a second area (a2) smaller than the first area (a1).

2. The internal reinforcement element (2) according to claim 1, which is entirely made of high-density polyethylene (PEHD) or high-density polyethylene reinforced with glass fibers.

3. Internal reinforcing element (2) according to claim 1 or 2, wherein said end surfaces (16) each comprise a network of axial protrusions (20).

4. Internal reinforcing element (2) according to claim 3, wherein said end surfaces (16) each comprise a set of openwork axial ribs (22) surrounding said network of axial protrusions (20).

5. The internal reinforcing element (2) according to claim 1 or 2, wherein The radial rib (8) network includes straight ribs (8a) and cylindrical ribs (8b) extending perpendicularly or parallel to the main axis (6), wherein the straight ribs (8a) define a shell having an overall shape of a rectangular parallelepiped between them, and the cylindrical ribs (8b) define a shell having an overall shape of a cylinder between them.

6. Internal reinforcing element (2) according to claim 1 or 2, wherein said radial ribs (8) form an asymmetric web.

7. Internal reinforcing element (2) according to claim 1 or 2, comprising clamping means (10) located on the side walls (12) of the central portion (4).

8. The internal reinforcing element (2) according to claim 1 or 2, wherein The end surface (16) has a shape corresponding hoxically to the annular sector, with a ratio k less than or equal to 1, in which shape each of the four corners of the end surface (16) is replaced by a rounded edge.

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

10. A method for producing a plastics material tank (24) for a motor vehicle, wherein: An internal reinforcement element (2) according to any one of claims 1 to 8 is welded to two opposing inner walls (26) of the tank (24).

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