Internal reinforcing elements for automotive plastic tanks

Abstract

The internal reinforcement element (2) of this plastic tank for motor vehicles is integrally realized, - a central part (4) having an arcuate cross-section, defining the main axis of the reinforcement element (2) and having a first area, the central part (4) including a rib network called a radial rib network (8) extending in a radial direction with respect to the main axis; - two axial ends (14) located on both sides of the central part (4) when viewed along the main axis, each axial end (14) having a curved oval end surface (16) which is included in the cross-section of the central part (4) and has a second area smaller than the first area; and includes.

Description

[Technical Field]

[0001] The present invention relates to an internal reinforcing element for a plastic automotive tank. The present invention also relates to a plastic automotive tank including an internal reinforcing element, and to a method for manufacturing a plastic automotive tank. [Background technology]

[0002] Traditionally, automotive fuel tanks are designed to store a certain amount of fuel at approximately atmospheric pressure. With the advent of hybrid electric vehicles, also known as HEVs (Hybrid Electric Vehicles), MHEVs (Mild-Hybrid Electric Vehicles), or PHEVs (Plug-in Hybrid Electric Vehicles), i.e., vehicles that include a combustion engine and one or more electric motors and can run for months without using the combustion engine, it is desirable to maintain pressure in the tank to reduce the passage of gasoline vapors through an activated carbon filter, also known as a canister. This is accomplished by isolating the canister from the tank using a valve, such as a Fuel Tank Isolation Valve (FTIV).

[0003] These plastic fuel tanks will fluctuate in size over their lifespan, first immediately after removal from the mold when the material shrinks as it cools, since they are made from extrusion blow-molded parisons, and then again during use due to thermal expansion during life, temperature changes over the course of a day, or over- or under-pressurization of the contents due to aging.

[0004] Plastic fuel tanks for automobiles, more specifically plastic fuel tanks for hybrid vehicles, typically include internal reinforcing elements in the form of struts connecting two opposing inner surfaces of the tank. These struts are required to withstand various tests, such as long-term aging tests or handling drop tests from a height of one meter, without impairing the properties of the fuel tank. For example, International Publication No. WO 2012 / 139962 discloses hourglass-shaped circular struts that are highly resistant to axial stresses resulting from tension / compression phenomena, as well as aging and durability tests. However, these struts are relatively vulnerable to stresses resulting from bending and / or torsion phenomena. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 139962 Summary of the Invention [Problem to be solved by the invention]

[0006] The main object of the present invention is to overcome these drawbacks of the prior art, and more specifically to provide an internal reinforcing element for a plastic tank for an automobile, which is capable of withstanding not only axial stresses resulting from tension / compression phenomena, but also bending and torsional phenomena, and which can be easily obtained by injection molding. [Means for solving the problem]

[0007] To this end, the present invention relates to an internal reinforcing element for a plastic tank for a motor vehicle, comprising: - a central portion having a cross section in the shape of a circular arc, defining a major axis of the reinforcing element and having a first area, the major axis passing through a center of rotation of the circular arc portion perpendicular to the circular arc portion, the central portion including a rib network, referred to as a radial rib network, the central portion extending in a radial direction relative to the major axis; two axial end portions located on either side of the central portion as viewed along the main axis, each axial end portion having a curved, oval end surface encompassed by a cross section of the central portion and having a second area smaller than the first area; The present invention is directed to an integrally realized internal reinforcing element, including

[0008] The curved shape of the central section and its rib structure allow the stresses transmitted to this element to be distributed in various directions, as shown by the results of analyses carried out by the inventors on the finished internal reinforcing element, which show that this type of internal reinforcing element is more resistant to bending and torsional phenomena than prior art struts characterized by a structure that can be described as unidirectional.

[0009] Furthermore, the curved shape of the internal reinforcing element helps to relieve it from stresses due to its location in the tank: for example, the concave portion of the internal reinforcing element can surround an accessory that is provided in the tank, so that all of this volume is not wasted, an arrangement that is not possible with prior art struts.

[0010] Furthermore, simulation tests have shown that if the end surface is not oval, i.e., if this surface has sharp corners, stresses will concentrate at these corners, which will create weak spots in the internal reinforcing element. The inventors have found that by replacing these sharp corners with rounded edges to create an oval shape, stresses are better distributed throughout the internal reinforcing element without concentrating at these rounded edges. Similar results have been observed in simulation tests of this type by reducing the cross section as you move from the center to the axial ends.

[0011] Advantageously, the internal reinforcing element is realized entirely in high density polyethylene (HDPE) or in high density polyethylene reinforced with glass fibres.

[0012] The internal reinforcing element is thus realized using a material that is easy to inject and weld and is inexpensive. To further improve the physical properties of the internal reinforcing element, for example, high density polyethylene can be reinforced with up to 10% by weight of glass fibers.

[0013] Advantageously, each of the end surfaces includes a network of axial projections.

[0014] The axial projections facilitate welding of the internal reinforcing element to the tank wall, among other things, they allow welding without preheating.

[0015] Preferably, each of the end surfaces includes a perforated assembly of axial ribs surrounding a network of axial projections.

[0016] The axial ribs, which are also intended to be welded to the tank wall, improve the holding strength of the weld of the internal reinforcing element to the tank wall by allowing air to escape during welding, in other words, they prevent air from accumulating between the axial end surface and the tank wall, which would weaken the bond between the internal reinforcing element and the tank.

[0017] Advantageously, the radial rib network includes straight ribs extending perpendicular or parallel to the major axis and defining generally rectangular parallelepiped-shaped recesses between each rib, and cylindrical ribs defining generally cylindrical-shaped recesses between each rib.

[0018] The radial rib network thus forms a network of blind holes in the central portion of the inner reinforcing element, giving the central portion a waffle-like shape. This type of network increases the stiffness of the inner reinforcing element. Furthermore, the radial rib network provides sound insulation to the inner reinforcing element by analogy with the acoustic properties of an egg carton.

[0019] Advantageously, the radial ribs form an asymmetric network.

[0020] In other words, the radial rib network is endowed with an error prevention function, also known as "poka-yoke" (to prevent careless mistakes) in Japanese, which forcibly determines the position and direction of the internal reinforcing elements inside the tank and prevents mistakes in assembling the internal reinforcing elements inside the tank, thereby reducing the waste rate in the manufacture of plastic tanks for automobiles.

[0021] Advantageously, the internal reinforcing element comprises gripping means located on the side walls of the central portion.

[0022] In this way, the internal reinforcing element has the means to be compatible with a variety of molding techniques, thereby facilitating the implementation of the present invention.

[0023] Advantageously, the end surface has a shape with rounded corners corresponding to a similar shape of a circular arc segment with a similarity ratio k less than or equal to 1. In other words, the end surface has a circular arc shape with rounded corners extending along an angular sector and a radius corresponding respectively to the angular sector and radius of the central circular arc segment multiplied by a similarity ratio k less than 1.

[0024] In addition to being easily realized, the end surfaces thus have a shape that is close to the cross section of the central portion, thus ensuring that the geometric transitions between the central portion and the ends do not have shapes that could concentrate stresses and weaken the internal reinforcing elements.

[0025] According to one particular embodiment of the invention, the arc shape of the cross section of the central portion has an infinite radius, and the curved oval shape of the end surface of each axial end also has an infinite radius, in other words the reinforcing element has a linear rather than a curved shape.

[0026] While linear shaped reinforcing elements do not offer the same advantages as curved shaped reinforcing elements, linear shaped reinforcing elements do offer the aforementioned advantages due to their elliptical shape and their decreasing cross section as they transition from the center to each axial end.

[0027] The present invention also contemplates a plastic tank for an automobile comprising an internal reinforcing element as defined above.

[0028] The invention also contemplates a method for manufacturing a plastic tank for a motor vehicle, in which an internal reinforcing element as defined above is welded to two opposing internal walls of the tank.

[0029] The invention will be better understood from the following description, given by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a perspective view of an internal reinforcing element of a plastic tank according to an embodiment of the present invention; FIG. [Figure 2] FIG. 2 is a front view of the internal reinforcing element of FIG. 1. [Figure 3] FIG. 2 is a cross-sectional view of the internal reinforcing element of FIG. 1. [Figure 4] FIG. 2 is an overhead view of the internal reinforcing element of FIG. 1. [Figure 5] 2 is a schematic view of a plastic tank for an automobile according to the present invention, including the internal reinforcing element of FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0031] 1 shows an internal reinforcing element 2 for a plastic tank for an automobile according to one embodiment of the present invention. The internal reinforcing element 2 is realized entirely in one piece from a material suitable for welding to the wall of the plastic tank. Here, the reinforcing element 2 is realized entirely from high-density polyethylene (HDPE) or high-density polyethylene reinforced with glass fibers.

[0032] The reinforcing element 2 includes a central portion 4 having a cross-section in the shape of a circular arc with respect to a major axis 6, which defines the axial direction of the reinforcing element 2. The major axis 6 is defined as an axis perpendicular to the circular arc and passing through the center of rotation of the circular arc. This is the axis of rotation of the circular arc. In other words, the major axis 6 extends outside the circular arc and the internal reinforcing element 2. Since the main characteristic of the major axis 6 according to the present invention is its direction and not its location, for the sake of clarity in the drawings, the major axis 6 is depicted as an axis extending within or on the surface of the internal reinforcing element 2. In other words, the axis designated "6" in each drawing is an axis parallel to the major axis 6 and thus indicates the axial direction. As best seen in the front view of the internal reinforcing element 2, which is the subject of FIG. 2, the central portion 4 includes a rib network, referred to as a radial rib network 8, which extends radially relative to the major axis 6.

[0033] The radial rib network 8 includes linear ribs 8a extending perpendicular or parallel to the main axis 6 and defining approximately rectangular parallelepiped recesses or blind holes between each rib. The radial rib network 8 also includes cylindrical ribs 8b defining approximately cylindrical recesses or blind holes between each rib. The linear ribs 8a contribute to the physical properties of the internal reinforcing element 2, particularly by improving its resistance to bending and torsion. The radial ribs 8b also contribute to, but do not limit, the physical properties of the internal reinforcing element 2. The radial ribs 8b form an asymmetric network that provides an anti-error function. In other words, the position of the radial ribs 8b allows the operator to install the internal reinforcing element 2 in the correct position and orientation within the tank, preventing installation in the wrong direction, which would compromise its optimal reinforcing function. 2, it can be seen that the central portion 4 of the internal reinforcing element 2 includes a radial rib 8b located on the equator of the central portion 4 and another radial rib 8b located away from the equator. The latter radial rib allows the operator to orient the internal reinforcing element 2 in the tank.

[0034] Figure 3 shows a cross-section of the internal reinforcing element 2, which shows the arcuate shape of the central portion 4. To this end, the blind holes defined by the radial rib network 8 are virtually filled in order to obtain a solid surface, as shown by the dashed line 9 in Figure 3. The cross-section of the central portion 4, imagined on a plane perpendicular to the main axis 6, has a first area a1.

[0035] Returning to Figure 2, the internal reinforcing element 2 comprises gripping means 10 located on the side walls 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 comprising a gripping means 10. Each of the gripping means 10 has the shape of a straight handle connected at two points to the corresponding side wall 12. The shape of the gripping means 10 can be likened to the shape of a handbag handle. The gripping means 10 facilitate the insertion of the internal reinforcing element 2 during the production of plastic tanks, particularly when this is achieved by blow molding using the technique of inserting the internal reinforcing element into the parison.

[0036] The internal reinforcing element 2 comprises two axial end portions 14 located on either side of the central portion 4 along the main axis 6. As best shown in FIG. 4, which is a top view of the internal reinforcing element 2, each axial end portion 14 has a curved, oval end surface 16 encompassed by the cross section of the central portion 4 and having a second area a2 smaller than the first area a1. The end surface 16 has a shape whose four corners are transformed into rounded edges 18, corresponding to the shape of the central arc portion with a similarity ratio k of 1 or less. Preferably, the similarity ratio k is selected from the group consisting of a value greater than 0.5, 0.8, and even 0.9. According to an equivalent definition, the end surface 16 has a circular arc shape whose four corners are transformed into rounded edges 18, extending along an angular sector and a radius corresponding, respectively, to the angular sector and radius of the central arc portion multiplied by a similarity ratio k less than 1. The end surfaces 16 are intended to be welded to two opposing walls of a plastic tank.

[0037] Each end surface 16 includes a network of axial projections 20 extending parallel to the main axis 6 over a length of 1 to 2 millimeters, where the axial projections 20 are arranged in radial rows and occupy the majority of the area of ​​the end surface 16. Each end surface 16 further includes a perforated assembly of axial ribs 22 surrounding the axial projection network 20, meaning that the axial ribs 22 define an outer edge that encompasses all of the axial projections 20. The axial ribs 22 are perforated to allow for air bleeds when the end surface 16 is welded to the tank wall, in other words there are gaps between the ribs.

[0038] The reinforcing element 2 is manufactured by an injection molding type method, and due to its geometry, in particular that of the radial rib network 8, the molding can be easily achieved in one operation.

[0039] 5 shows a plastic tank 24 according to the invention. The tank 24 includes an internal reinforcing element 2, which is welded to two opposing walls 26 of the tank 24. Welding of the internal reinforcing element 2 to the tank walls 26 can be achieved using any suitable technique during or after molding of the tank 24. The gripping means 10 may be secured by a holding member (not shown) to facilitate welding of the reinforcing element 2 to the tank walls 26.

[0040] The present invention is not limited to the embodiments presented, and other embodiments will be apparent to those skilled in the art. [Explanation of symbols]

[0041] 2 Internal reinforcement elements 4 Central part 6 main axis 8 Radial Rib Network 8a straight ribs 8b Cylindrical rib 9 Dashed Line 10 Gripping means 12 Side wall 14 Axial end 16 End surface 18 Rounded Edges 20 Axial projection network 22 Axial rib 24 Tank 26 Tank Wall

Claims

1. An internal reinforcing element (2) for a plastic tank for an automobile, comprising: a central portion (4) defining a main axis (6) of said reinforcing element (2) and including a cross section in the shape of a circular arc having a first area (a 1 ) in a plane perpendicular to said main axis (6), The main axis (6) is perpendicular to the cross section of the arcuate shape and passes through the center of the circle of which the arcuate shape forms a part, said central portion (4) including a rib network, referred to as a radial rib network (8), extending radially relative to said main axis; - two axial end portions (14) located on either side of the central portion (4) in a direction parallel to the main axis (6), each of the axial end portions (14) having a first area (a) encompassed by a cross section of the central portion (4) when viewed in a direction parallel to the main axis (6); １ ) smaller than the second area (a ２ an axial end (14) having a curved oval end surface (16) with a An integrally realized internal reinforcing element (2) comprising:

2. 2. A reinforcing element (2) according to claim 1, which is realized entirely in high density polyethylene (HDPE) or in high density polyethylene reinforced with glass fibres.

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

4. A reinforcing element (2) according to claim 3, wherein each of said end surfaces (16) comprises a perforated assembly (22) of axial ribs surrounding said axial projection network (20).

5. 3. A reinforcing element (2) according to claim 1 or 2, wherein the radial rib network (8) comprises straight ribs (8a) extending perpendicular or parallel to the main axis (6) and defining between each rib a generally rectangular parallelepiped recess, and cylindrical ribs (8b) defining between each rib a generally cylindrical recess.

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

7. A reinforcing element (2) according to claim 1 or 2, comprising gripping means (10) located on the side walls (12) of said central part (4).

8. 3. A reinforcing element (2) according to claim 1 or 2, wherein the end surface (16) has a shape corresponding to a similar shape of the circular arc shape with a similarity ratio k of 1 or less, the four corners of which are rounded.

9. A plastic tank (24) for an automobile comprising a reinforcing element (2) as described in claim 1 or 2.

10. 3. A method for manufacturing a plastic tank (24) for an automobile, comprising welding a reinforcing element (2) according to claim 1 or 2 to two opposing inner walls (26) of the tank (24).

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