Internal reinforcing element for plastic material tank of motor vehicle

Abstract

An internal reinforcement element (2) for a tank of plastic material for a motor vehicle is made as a single part and comprises:-a central portion (4) having a cross-section of an annular sector defining a main axis of the reinforcement element (1) and having a first area, the central portion (4) comprising a web of ribs, referred to as a web of radial ribs (8), extending radially with respect to the main axis, and-two axial ends (14) located on either side of the central portion (4) with respect to the main axis, each 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 an internal reinforcement element and to a method for manufacturing a tank made of plastic material for a motor vehicle. Background Art

[0002] Traditionally, the fuel tanks of motor vehicles are designed to keep the fuel at a pressure almost equal to atmospheric pressure. With the advent of hybrid vehicles, also called HEV (hybrid electric vehicle), MHEV (mild hybrid electric vehicle) or PHEV (plug-in hybrid electric vehicle), in other words, motor vehicles comprising a heat engine and one or more electric motors, which may run for months without the use of the heat engine, it is preferred to maintain the pressure in the fuel tank in order to reduce the escape of gasoline vapors through the activated carbon filter (also called canister). This is achieved by isolating the canister from the fuel tank using, for example, a fuel tank isolation valve (FTIV).

[0003] Such fuel tanks made of plastic material are therefore subject to dimensional changes during their service life. Such plastic tanks are obtained by extrusion blow molding of a parison, first of all, after the plastic tank is removed from the mold, cooling occurs with material shrinkage, and also during its use, in particular due to overpressure or underpressure of its contents, or due to thermal expansion during its service life, or due to temperature changes caused by daily cycles, or due to its aging.

[0004] Typically, fuel tanks made of plastic material for motor vehicles, more particularly for hybrid motor vehicles, comprise internal reinforcement elements in the form of struts that connect two opposing inner surfaces of the fuel tank. Such struts must withstand various tests, such as long-term aging or a "carrying drop" from a height of 1 meter, without reducing the performance of the fuel tank. Thus, document WO 2012 / 139962 A1 discloses a circular strut in the form of an hourglass that is very resistant to axial stresses caused by tension / compression phenomena and aging and strength tests. However, such struts are relatively sensitive to stresses caused by bending and / or torsion phenomena. Summary of the invention

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

[0006] To this end, the subject of the invention is an internal reinforcement 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 to it, 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 ends, located on either side of the central portion relative to the main axis, each axial end having an elliptical and curved end surface, the end surface being inscribed or inscribed in the 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 enable the stresses transmitted to the internal reinforcement element to be better distributed in different directions, as has been demonstrated by the finite element analysis carried out by the inventors. It can be understood that such an internal reinforcement element is better able to resist bending and torsion phenomena than the struts of the prior art, which are characterized by a structure that can be described as unidirectional.

[0010] Furthermore, the curved shape of the internal reinforcing element allows it to better overcome the constraints (limitations) related to its positioning in the tank. For example, the concave portion of the internal reinforcing element can be used to be arranged around an accessory in the tank, so that the volume of this concave portion is not completely lost. The pillars of the prior art do not allow this type of arrangement to be achieved.

[0011] Furthermore, simulation tests made it possible to determine that if the end surface is not elliptical, that is, if it has protruding (convex) corners (angles), stress concentrations are observed at these corners, thus forming weak areas of the internal reinforcing element. The inventors have found that by replacing these protruding corners with rounded edges (rounded corners), thus forming an elliptical shape, a better distribution of stresses over the entire internal reinforcing element is observed, without the stresses being concentrated on these rounded edges. Such simulation tests also made it possible to observe similar results due to the narrowing of the cross section in the transition (extension) from the central part to the axial end.

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

[0013] Thus, the internal reinforcement element is 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 protrusions make it possible to facilitate the welding of the internal reinforcing element to the wall of the tank. In particular, they make it possible to perform the 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 also used for welding to the wall of the tank improve the strength of the weld of the internal reinforcing element to the wall of the tank 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 lead to a weakening of 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 housing of substantially rectangular hexahedral shape, and cylindrical ribs defining between them a housing of substantially cylindrical shape.

[0019] Thus, the radial rib network forms a network of blind holes in the central portion of the internal reinforcement element, thereby giving the central portion a general waffle shape. Such a network can improve the rigidity of the internal reinforcement element. Furthermore, the radial rib network imparts an anti-noise effect to the internal reinforcement element in a manner similar to the acoustic properties of an egg crate.

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

[0021] The radial rib network thus has a poka-yoke function, also expressed by the Japanese term "poka yoke", meaning respectively "unintentional error" and "prevention", 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 installation errors of the internal reinforcing element in the tank.

[0022] Advantageously, the internal reinforcing element comprises clamping means located 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 making the invention easy to implement.

[0024] Advantageously, the end surface has a shape corresponding to the homology 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 part, 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 reinforcement 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 from 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 A cross-sectional view of an 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 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 a 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 internal reinforcing element 2. For the sake of clarity of the accompanying drawings, the main axis 6 is shown by an axis extending in the internal reinforcing element 2 or on the surface of the internal reinforcing element 2, since the main property of the main axis 6 according to the invention is its direction rather than its position. In other words, the axis with the reference numeral "6" in the accompanying 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 , which network of ribs is called radial ribs 8 .

[0038] The radial rib 8 net includes straight ribs 8a, which extend perpendicularly or parallel to the main axis 6 and define a roughly rectangular parallelepiped-shaped shell or blind hole between the straight ribs 8a. The radial rib 8 net also includes cylindrical ribs 8b, which define a roughly cylindrical shell or blind hole between them. The straight ribs 8a help to improve the mechanical properties of the internal reinforcement element 2, particularly by improving its bending resistance and torsion resistance. The radial ribs 8b also help to 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 error proofing. In other words, the position of the radial ribs 8b allows the operator to correctly position and orient the internal reinforcement element 2 so that it can be installed in the tank so that it will not be installed in reverse, in which case it may not be able to perform its reinforcing function in the best way. In this example, it can be seen that the central part 4 of the internal reinforcement element 2 includes a radial rib 8b located on the equator of the central part 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. To this end, the blind holes defined by the network of radial ribs 8 are notionally 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 the side wall 12 of the central part 4. In this embodiment of the invention, the central part 4 of the reinforcing element 2 comprises two opposite 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 of the corresponding side wall 12. The shape of these clamping devices 10 can be compared (compared) to the shape of a briefcase handle. The clamping devices 10 are able to 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 implementing a technique of inserting the internal reinforcing element into a parison.

[0041] The inner reinforcing element 2 comprises two axial ends 14, which are located on either side of the central portion 4 relative to the main axis 6. Figure 4 As better shown in Figure 41 is a top view of an internal reinforcing element 2, each axial end 14 having an elliptical (or rectangular) and curved end surface 16 inscribed (or inscribed) in the cross section of the central part 4, the end surface 16 having a second area a2 less than the first area a1. Here, the end surface 16 has a shape corresponding to the homology (similarity, in French homothétie) of an annular sector of the central part, with a ratio k less than or equal to 1, wherein each of the four corners is replaced by a fillet (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 surface 16 has the shape of an annular sector, extending over an angular sector and a radius corresponding respectively to the angular sector and the radius of the annular sector of the central part multiplied by a ratio k less than 1, the four corners of which are replaced by fillet edges 18. The end surface 16 is intended to be welded to two opposite walls of the plastic tank.

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

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

[0044] Figure 5 2 shows a tank 24 made of plastic material according to the invention. The tank 24 comprises an internal reinforcing element 2 welded to two opposite walls 26 of the tank 24. The internal reinforcing element 2 may 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 may be clamped by a retaining member (not shown) to facilitate welding of the reinforcing element 2 to the walls 26 of the tank.

[0045] The 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 rib mesh

[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 a main axis (6) of the reinforcing element (2) and having a first area (a1), the main axis (6) passing through the centre of rotation of the annular sector and being perpendicular to the same, the central portion (4) comprising a network of ribs extending radially with respect to the main axis, which network of ribs is called a network of radial ribs (8), and - two axial ends (14) located on either side of the central portion (4) relative to the main axis (6), each axial end (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. Reinforcing element (2) according to the preceding claim, said reinforcing element (2) being entirely made of high-density polyethylene (PEHD) or of high-density polyethylene reinforced with glass fibres.

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

4. Reinforcing element (2) according to the preceding claim, wherein said end surfaces (16) each comprise a set of perforated axial ribs (22) surrounding said network of axial protuberances (20).

5. Reinforcing element (2) according to any one of the preceding claims, 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. Reinforcing element (2) according to any one of the preceding claims, in which said radial ribs (8) form an asymmetric web.

7. Reinforcing element (2) according to any one of the preceding claims, comprising clamping means (10) located on the side walls (12) of the central portion (4).

8. Reinforcing element (2) according to any one of the preceding claims, wherein The end surface (16) has a shape corresponding 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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