DE102016220693A1 - Tank stiffening element for a fuel tank - Google Patents

Abstract

Tank stiffening element (2) for a fuel tank (4), wherein the tank stiffening element (2) is at least partially made of a foamable plastic (30), with at least one foamed area (10) in which the foamable plastic (30) is foamed.

Description

The present invention relates to a tank stiffening element for a fuel tank.

Tank stiffeners for fuel tanks, also called "stand-off", are used, for example, to structurally reinforce the fuel tanks of hybrid vehicles. Fuel tanks of hybrid vehicles must withstand increased internal pressure, which may mean an overpressure of up to 350 mbar. The deformation of the fuel tank under internal pressure is to be kept within predetermined limits, including the tank stiffening elements are used.

In order to withstand the internal pressure, there is a demand to design the tank stiffening elements as stiff and massive as possible. In particular, in the area of a connection of the tank stiffening elements to an inner wall of the fuel tank, however, there is a risk that it comes through the tank stiffening elements in the event of a crash to an Austanzen the tank wall and thus destroying the tank bladder. In order to ensure the integrity of the tank bladder in the event of a crash and to prevent leakage of fuel, tank stiffening elements, for example, predetermined breaking points, or are designed by joints such that in the event of a crash, a certain flexibility is ensured to avoid destroying the tank wall.

Against this background, the invention is based on the technical problem to provide an improved tank stiffening element for a fuel tank, which is inexpensive to produce, allows reliable stiffening of a fuel tank and in particular reduces the risk of fuel leakage in the event of a crash. This object is achieved by a tank stiffening element according to claim 1 and a tank stiffening element according to claim 8. Further embodiments of the invention will become apparent from the dependent claims and the description below.

According to a first aspect, the invention relates to a tank stiffening element for a fuel tank, wherein the tank stiffening element is at least partially made of a foamable plastic, with at least one foamed area in which the foamable plastic is foamed.

Due to the fact that the tank stiffening element has a foamed area, a local weakening of the tank stiffening element in the foamed area can be intentionally introduced, for example, in an injection molding process. Thus, the foamed area may have a higher elasticity and / or a lower strength compared to other adjacent areas of the tank stiffening element. The tank stiffening element can therefore be adapted specifically to the static and dynamic loads during operation and also be manufactured inexpensively and in particular in one piece.

For example, the tank stiffening element can be manufactured in one piece by injection molding in a single shot. Thus, a cost-effective production of the tank stiffening element can be ensured.

In the injection molding process, a local weakening or a local softening can be deliberately set in the foamed region, wherein the tank stiffening element in this region has, for example, a lower modulus of elasticity than in regions adjacent to the foamed region.

According to a further embodiment, the tank stiffening element has connecting sections, wherein the connecting sections are provided for connecting the tank stiffening element to a fuel tank, the foamed area being arranged between the connecting sections, wherein the connecting sections are at least partially made of the foamable plastic, and wherein the foamable plastic of the foamed area has a lower density than the foamable plastic of the connecting portions.

The connecting sections are in particular designed to be welded to inner walls of a fuel tank. Thus, a first connecting portion of the stiffening element may be provided to be welded to a first inner wall of a first half-shell of the fuel tank. Accordingly, a second connecting portion of the tank stiffening member may be provided to be welded to a second inner wall of a second half-shell of a fuel tank.

The half-shells of a fuel tank can be designed in multiple layers. Thus, the half shells can have three or more layers, wherein in particular a barrier layer can be sandwiched on two sides by at least two layers. The barrier layer may be formed as a diffusion barrier for hydrocarbons. In particular, a half-shell may have a five-layer wall structure.

In combination with a subject tank stiffening element, the risk of delamination, ie a local dissolution of the Layer composite of the wall structure, be reduced in the event of a crash.

In particular, the tank stiffening element has two opposite end faces, which are provided at opposite ends of the tank stiffening element at the connecting portions. The end surfaces are adapted to be welded to connecting portions of a fuel tank. In this way, a cost-effective, reliable and simple connection of the tank stiffening element to a fuel tank can take place.

Due to the lower density of the foamable plastic in the foamed area, the foamed area can have a higher elasticity and a lower modulus of elasticity than the foamable plastic of the connecting sections.

The connecting portions may be made of a foamable plastic, which is foamed to a lesser extent, than the foamable plastic of the foamed area.

According to a further embodiment of the tank stiffening element, it is provided that the connecting sections and / or the foamed area viewed along a longitudinal direction have a constant cross-sectional shape and / or a constant cross-sectional area.

According to a further embodiment of the tank stiffening element is provided that the tank stiffening element consists of the foamable plastic.

The tank stiffening element can accordingly consist of a single plastic which has been selectively foamed in the foamed area. For example, the tank stiffening element can be inexpensively manufactured in one piece or in one piece by injection molding.

The tank stiffening element may for example consist of a foamable polymer, such as HDPE, POM, PA or the like. The polymer may, for example, have been loaded with an inert gas, in particular nitrogen, as blowing agent in order to be foamed locally during the injection molding process in the foamed region.

The foaming can be done by physical foaming or chemical foaming.

1. a) Einspritzen des aufschäumbaren Kunststoffs in eine Kavität einer Spritzgussform, wobei der aufschäumbare Kunststoff mit einem Treibmittel beladen ist;
2. b) lokale Vergrößerung der Kavität.

According to a further embodiment of the tank stiffening element, the tank stiffening element has been produced according to a method with the following method steps:

1. a) injecting the foamable plastic into a cavity of an injection mold, wherein the foamable plastic is loaded with a propellant;
2. b) local enlargement of the cavity.

By means of the injection molding method described above, the local change in property can be adjusted in a targeted manner in a foamed region in which the injection molding cavity is locally enlarged.

Prior to the local enlargement of the cavity, a complete filling of the cavity with the foamable plastic can take place. Alternatively or additionally, before the local enlargement of the cavity, a holding pressure phase for filling the cavity can be provided.

The local enlargement of the cavity can be effected by an opening movement of a mold slide or several mold slides of an injection mold. Thus, a mold slide can be moved in a direction away from the cavity filling the foamable plastic to release further space for expansion or foaming of the plastic and to increase the cavity. For example, the injection mold may have two oppositely disposed mold slides which can be moved apart in opposite directions for local enlargement of the cavity.

The foamed area may be arranged in a central central portion of the tank stiffening element. Thus, for example, two connecting portions may be provided, which extend from a central, foamed area projecting in opposite directions. The connecting sections may each extend over identical longitudinal dimensions along a longitudinal axis, so that the tank stiffening element is configured in particular mirror-symmetrically to a central center plane. In this way, a homogeneous load of the tank stiffening element and adjacent tank wall sections can be achieved.

Alternatively, the foamed area can be arranged with an offset to a central center plane. Thus, for example, two connecting sections may be provided, which extend from a decentralized, foamed area projecting in opposite directions. The connection sections can each extend over different longitudinal dimensions along a longitudinal axis, so that the tank stiffening element is in particular designed asymmetrically to a central center plane. Thus, the geometry of the tank stiffening element can be adapted to the expected operating loads.

By virtue of the fact that the tank stiffening element is given increased flexibility or elasticity by a local change in property in the foamed area, the cross-section of the tank stiffening element can be kept substantially constant along its entire length, so that no local tapering or constriction of the tank stiffening element has to take place along its longitudinal extent, to provide increased elasticity in the event of a crash.

Alternatively, the connecting portions and / or the foamed portion may have a bulge or taper viewed along a longitudinal direction. Thus, the geometry of the tank stiffening element can be adapted to the expected operating loads.

A tank stiffening element may be provided, wherein the foamed area or the plastic of the foamed area has a low modulus of elasticity, as an area adjacent to the foamed area or the plastic of the area adjoining the foamed area. Such an adjacent region can be, for example, one or more connecting sections which are provided for connecting the tank stiffening element to a fuel tank. Thus, the material properties of the tank stiffening element can be adapted to the expected operating loads.

In particular, the modulus of elasticity of the area adjacent to the foamed area may be greater by a factor of 1.5 or more than the modulus of elasticity of the foamed area. For example, the modulus of elasticity of the plastic of the foamed portion may be 1000 MPa, while the modulus of elasticity of the plastic of the portion adjacent to the foamed portion is 1500 MPa or more.

According to a further aspect, the invention relates to a tank stiffening element for a fuel tank, with connecting sections and with a decoupling area, wherein the connecting sections are provided for connecting the tank stiffening element to the fuel tank, wherein decoupling area is arranged between the connecting sections, wherein the connecting sections comprise a first plastic, wherein the decoupling region comprises a second plastic, wherein the decoupling region has been positively and / or materially connected to the connecting portions by a multi-component injection molding process.

By producing the tank stiffening element in the multi-component injection molding process, a local change in the component properties relative to the connecting sections can be achieved in the decoupling region in a targeted manner. For example, a desired elasticity or a predetermined breaking point can be introduced through the second material into the tank stiffening element.

As a multi-component injection molding, for example, the Coreback technique, the turntable technology, the insert technology or the Umsetztechnik can be used. By overmolding, overmolding, injection molding and / or injection molding of the plastics to be joined in the multi-component injection molding process, a cohesive and / or positive locking and / or non-positive connection between the decoupling region and the connecting sections can be produced in a simple manner.

According to a further embodiment, a tank stiffening element may be provided, wherein the first plastic has a higher modulus of elasticity than the second plastic, in particular that the modulus of elasticity of the first plastic has an modulus of elasticity which is by a factor of 1.5 or more greater than the modulus of elasticity of the second plastic. Thus, the material properties of the tank stiffening element can be adapted to the expected operating loads. For example, the modulus of elasticity of the second plastic may be 1000 MPa while the modulus of elasticity of the second plastic is 1500 MPa or more.

The first and / or the second plastic may be made of a polyethylene, polyamide, rubber or polyoxymethylene.

For example, the first plastic is a polyamide and the second plastic is a polyethylene. Further, for example, the first plastic may be a polyamide, polyethylene, polyoxymethylene or a polyamide, while the second plastic is a rubber, in particular a synthetic or natural rubber.

According to alternative embodiments, it can be provided that the second plastic is a particularly brittle plastic that is more brittle than the first plastic in order to provide a predetermined breaking point on the tank stiffening element.

Overall, an improved, tank reinforcing element for a fuel tank can thus be specified by the invention, which is inexpensive to produce, enables reliable stiffening of a fuel tank and in particular reduces the risk of fuel leakage in the event of a crash.

• 1 ein Tankversteifungselement im fertig montierten Zustand;
• 2 Querschnittsformen eines Tankversteifungselements;
• 3 ein Tankversteifungselement in einer Spritzgussform;
• 4 ein weiteres Tankversteifungselement im fertig montierten Zustand.

The invention will be described in detail with reference to an exemplary embodiments illustrative drawing. Each show schematically:

• 1 a tank stiffening element in the assembled state;
• 2 Cross-sectional shapes of a tank stiffening element;
• 3 a tank stiffener in an injection mold;
• 4 another tank stiffening element in the assembled state.

1 shows a tank stiffening element according to the invention 2 for a fuel tank 4 , In 1 is a partial section through a provided with multiple stiffening fuel tank 4 shown. The fuel tank 4 has an upper half shell 6 and a lower half shell 8th ,

The tank stiffening element 2 is made of a foamable plastic. The tank stiffening element 2 has a foamed area 10 on, in which the foamable plastic is foamed.

The tank stiffening element 2 has connecting sections 12 . 14 , The connecting sections 12 . 14 are for connecting the tank stiffening element 2 the fuel tank 4 or its half-shells 6 . 8th intended.

The foamed area 10 is between the connection sections 12 . 14 arranged. The connecting sections 12 . 14 are in this case made of the foamable plastic. The foamable plastic of the foamed area 10 has a lower density than the foamable plastic of the connecting portions 12,14. In this way, the mechanical properties of the tank stiffening element 2 in the foamed area 10 been specifically changed. So has the foamed area 10 a lower modulus of elasticity and a higher elasticity than the adjacent connecting portions 12 . 14 ,

The connecting sections 12 . 14 are interconnected via the foamed area. connecting portion 12 is cohesively with a connecting section 16 the upper half shell 6 of the fuel tank 4 connected. connecting portion 14 is with a connection section 18 the lower half shell 8th of the fuel tank 4 connected. The connection of the connection section 12 and the connection section 16 , or the connection section 14 and the connection section 18 , has been formed in each case as a material connection by welding.

The connecting sections 16 . 18 the upper half shell 6 or the lower half shell 8th each have radii 20 or fillets 20 to provide a notch effect or load spikes or delamination when transmitting tensile forces across the tank stiffener 2 to avoid.

2 shows an example of possible cross-sectional shapes of a tank stiffening element 2 out 1 along the in 1 illustrated section line II. The tank stiffening element 2 can along a longitudinal direction or along a longitudinal axis L considered to have a constant cross-sectional shape and / or a constant cross-sectional area. The tank stiffening element 2 For example, it can be circularly made of solid material ( 2A ). The tank stiffening element 2 may have an annular cross section ( 2 B ). The tank stiffening element 2 may have a polygonal cross-sectional shape, for example a quadrangular or square cross-sectional shape ( 2C ). The stiffening element 2 can have ribs or web-like structures to the transverse and / or bending elasticity of the tank stiffening element 2 specifically adapted to the load cases occurring during operation. ( 2D . 2E . 2F ).

The tank stiffening element may, for example, webs 22 or struts 22 exhibit ( 2D . 2E . 2F . 2G ).

The bridges 22 or struts 22 can each end at opposite ends in an end face 24 converge as the connecting portion for connecting the tank stiffening element 2 with connecting sections 16 . 18 a fuel tank 4 serve ( 2G ).

1. a) Einspritzen eines aufschäumbaren Kunststoff 30 in eine Kavität 26 einer Spritzgussform 28 (3);
2. b) lokale Vergrößerung der Kavität 26.

As discussed above, the tank stiffening element 2 inexpensive and easy to be produced in an injection molding process. For example, the following process steps are performed:

1. a) injecting a foamable plastic 30 in a cavity 26 an injection mold 28 ( 3 );
2. b) local enlargement of the cavity 26 ,

The in the injection mold 28 or the cavity 26 injected the molten plastic 30 , in this case HDPE, is loaded with nitrogen as propellant. The injection mold has two half shells 32 . 34 , each mold slide 36 . 38 exhibit. After the cavity 26 completely with the plastic 30 has been filled, there is a Nachdruckphase to compensate for shrinkage of the plastic and a complete filling of the cavity 26 to ensure.

The first in the cavity 26 indented form slider 36 . 38 are now moved apart in opposite directions, as indicated by the arrows in 3 shown. This way, the cavity becomes 26 locally enlarged. The initially liquid or dissolved nitrogen passes through this local enlargement of the cavity 26 and the associated pressure drop from the liquid to the gas phase and causes in this way a local foaming of the plastic 30 in the area of enlarge cavity. In this way, the mechanical properties of a tank stiffening element to be produced can be adjusted in a targeted manner.

As in 3 As is indicated, the foamed region is produced in a central middle region of the tank stiffening element, so that the tank stiffening element is essentially mirror-symmetrical to a central center plane M is designed. The connecting sections 12 . 14 the finished tank stiffening element 2 therefore point along the longitudinal axis L measured an identical length measure.

In 4 is another stiffening element 40 for a fuel tank 4 shown. The stiffening element 40 has connecting sections 42 . 44 and a decoupling area 46 , The connecting sections 42 . 44 are for connecting the tank stiffening element 40 with the fuel tank 4 intended. The fuel tank 4 again has an upper half-shell 6 and a lower half shell 8th on, wherein the half-shells 6,8 each connecting sections 16 . 18 are assigned to the stiffening element 40 to tie. Between the connecting sections 16, 18 and the connecting sections 42 . 44 of the tank stiffening element 40 In turn, a cohesive connection has been produced by welding.

The decoupling area 46 is between the connection sections 42 . 44 arranged. The connecting sections 42 . 44 have a first plastic and the decoupling area 46 has a second plastic. The decoupling area 46 is by a multi-component injection molding process form-fitting and cohesively with the connecting portions 42 . 44 been connected. The second plastic has in this case a lower modulus of elasticity and a higher elasticity than the first plastic. The modulus of elasticity of the first plastic is greater by a factor of 1.5 than the modulus of elasticity of the second plastic.

According to alternative embodiments, it can be provided that the second plastic is a particularly brittle plastic that is more brittle than the first plastic, around a predetermined breaking point on the tank stiffening element 40 provided.

LIST OF REFERENCE NUMBERS

2

Tank stiffener

4

Fuel tank

6

upper half shell

8th

lower half shell

10

foamed area

12

connecting portion

14

connecting portion

16

connecting portion

18

connecting portion

20

Radius, fillet

22

Webs, strut

24

face

26

cavity

28

injection mold

30

foamable plastic

32

half shell

34

half shell

36

shape shifter

38

shape shifter

40

stiffener

42

connecting portion

44

connecting portion

46

decoupling region

L

longitudinal axis

M

midplane

Claims (12)

Tank stiffening element (2) for a fuel tank (4), - wherein the tank stiffening element (2) is at least partially made of a foamable plastic (30), - With at least one foamed area (10), in which the foamable plastic (30) is foamed. Tank stiffening element after Claim 1 , - with connecting sections (12, 14), - the connecting sections (12, 14) being provided for connecting the tank stiffening element (2) to a fuel tank (4), - the foamed section (10) being arranged between the connecting sections (12, 14), - the connecting sections (12, 14) are at least partially made of the foamable plastic (30), and - wherein the foamable plastic (30) of the foamed area (10) has a lower density than the foamable plastic (30) of the connecting portions (12, 14). Tank stiffening element according to one of the preceding claims, - Wherein the tank stiffening element (2) consists of the foamable plastic (30). A tank stiffener as claimed in any one of the preceding claims made according to a method comprising the following steps: a) injecting the foamable plastic (30) into a cavity (26) of an injection mold (28), wherein the foamable plastic (30) is loaded with a blowing agent; b) local enlargement of the cavity (26). Tank stiffening element after Claim 4 , wherein before step b) - a complete filling of the cavity (26) with plastic (30) takes place; and / or - a holding pressure phase for filling the cavity (26) is provided. Tank stiffening element according to one of Claims 4 or 5 , - wherein the local enlargement of the cavity by an opening movement of a mold slide (36, 38) or more mold slides (36, 38) takes place. Tank stiffening element according to one of the preceding claims, - Wherein the connecting portions (12, 14) and / or the foamed portion (10) along a longitudinal direction (L) viewed as having a constant cross-sectional shape and / or a constant cross-sectional area; or - Wherein the connecting portions (12, 14) and / or the foamed area (10) viewed along a longitudinal direction (L) having a bulge or taper. Tank stiffening element according to one of the preceding claims, - wherein the foamed area (10) has a low modulus of elasticity, as an area adjacent to the foamed area (12, 14), in particular, - That the modulus of elastic of the area adjacent to the foamed area (12, 14) by a factor of 1.5 or more is greater than the modulus of elasticity of the foamed area (10). Tank stiffening element according to one of the preceding claims, - The foamed area is arranged mirror-symmetrically to a central plane (M); or - Wherein the foamed area is arranged with an offset to a center plane (M). Tank stiffening element for a fuel tank, - With connecting sections (42, 44) and with a decoupling area (46), - wherein the connecting portions (42, 44) are provided for connecting the tank stiffening element (40) with the fuel tank (4), - wherein decoupling region (46) between the connecting portions (42, 44) is arranged, - wherein the connecting portions (42, 44) have a first plastic, - wherein the decoupling region (46) comprises a second plastic, - Wherein the decoupling region (46) by a multi-component injection molding method has been positively and / or materially connected to the connecting portions (42, 44). Tank stiffening element after Claim 10 , - wherein the first plastic has a higher modulus of elasticity than the second plastic, in particular, - that the modulus of elasticity of the first plastic has an E-modulus which is greater by a factor of 1.5 or more than the modulus of elasticity of the second plastic. Tank stiffening element according to one of Claims 10 or 11 , - wherein the first and / or the second plastic made of a polyethylene, polyamide, rubber or polyoxymethylene.

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