DE102021116677A1 - Process for manufacturing a fuel tank - Google Patents

Abstract

Method for manufacturing a fuel tank with nested shells made of plastic and metal, characterized by the following steps:- molding two composite half-shells (10, 12), each with an outer half-shell (14) made of metal and an inner half-shell (16) made of plastic, and - Assembling the two composite half-shells edge-to-edge and joining the edges of the inner half-shells (16) and the edges of the outer half-shells (14).

Description

The invention relates to a method for producing a fuel tank with nested shells made of plastic and metal, and to a fuel tank produced using this method.

In particular, the invention relates to a method for producing a fuel tank for plug-in hybrid vehicles, in which temperature fluctuations can lead to significant pressure fluctuations inside the tank, particularly during long journeys in electric mode, so that the tank must be able to withstand an increased internal pressure and possibly also a certain negative pressure. Other requirements that such a tank must meet are crash safety, in particular with regard to possible electrical discharges, tightness, low permeability for fuel vapors, chemical resistance and noise behavior (NVH; Noise Vibration Harshness).

Out of WO 2014/058331 A a two-shell tank is known in which an inner shell made of metal is surrounded by a shell made of plastic.

The object of the invention is to create a method for producing a tank that can better meet the special requirements in a plug-in hybrid vehicle.

• - Formen zweier Verbundhalbschalen mit je einer äußeren Halbschale aus Metall und einer inneren Halbschale aus Kunststoff, und
• - Aneinandersetzen der beiden Verbundhalbschalen Rand-zu-Rand und Fügen der Ränder der inneren Halbschalen sowie der Ränder der äußeren Halbschalen.

This object is achieved according to the invention by a method with the following steps:

• - Molding of two composite half-shells, each with an outer half-shell made of metal and an inner half-shell made of plastic, and
• - Assembling the two composite half-shells edge to edge and joining the edges of the inner half-shells and the edges of the outer half-shells.

In the tank produced in this way, an inner shell made of plastic is encapsulated in an outer shell made of metal, so that high pressure resistance can be achieved due to the high tensile strength of the metal, for example stainless steel. Since the half-shells made of plastic and metal each form a composite half-shell, i.e. the plastic adheres to the metal wall of the outer shell, the tank can also withstand occasional negative pressure, especially since, depending on the shape of the tank, the low compressibility of the plastic material usually leads to a collapse in one direction the dimensions of the tank tend to increase in another direction, but this is prevented by the metal shell tightly enclosing the inner tank. At the same time, the outer tank, which acts as a Faraday cage, and the electrically insulating inner tank reduce the risk of the fuel igniting due to electrical discharges in the event of a crash.

A further advantage of the design proposed here is that when the inner half-shells are formed from plastic in one operation, built-in components such as baffles, holders for functional parts or the like can also be formed.

Advantageous refinements and developments of the invention are specified in the dependent claims.

In one embodiment, the inner half-shells made of plastic and the outer half-shells made of metal are formed together in a single forming step and connected to form a composite half-shell. In another embodiment, the metal outer half-shell is first formed, for example by compression molding or deep drawing, and this half-shell is then used as a sort of mold tool for forming the plastic inner half-shell "in situ".

The edges of the inner half-shells made of plastic can be joined, for example by thermal welding or ultrasonic welding or possibly also by gluing, while the inner half-shells are fixed in the outer half-shells and held in position by them. A further step for joining the edges of the outer metal half-shells, for example by thermal welding, laser welding, gluing, or crimping, can then follow immediately or possibly also take place simultaneously with the joining of the inner half-shells. The heat generated during the welding of the outer half-shells can also be used to weld the inner half-shells made of plastic.

The material for the inner half-shells can be a thermoplastic, in particular a long-fiber-reinforced thermoplastic.

In one embodiment, the outer half-shells can also have certain undercuts or openings in selected positions, which result in close interlocking between metal and plastic when the inner half-shells are formed from plastic.

Exemplary embodiments are explained in more detail below with reference to the drawing.

• 1 einen Schnitt durch einen Kraftstofftank, der nach einem erfindungsgemäßen Verfahren hergestellt ist;
• 2 einen Schnitt durch eine Halbschale aus Metall;
• 3 einen Schnitt durch ein Unterwerkzeug und die darin eingelegte Halbschale aus Metall;
• 4 das Unterwerkzeug und die Halbschale nach 3 zusammen mit einer mittels eines Oberwerkzeugs in die Halbschale aus Metall eingeformten inneren Halbschale aus Kunststoff;
• 5 ein Werkzeug zum gemeinsamen Umformen von Rohlingen aus Metall und Kunststoff gemäß einer anderen Ausführungsform des Verfahrens;
• 6 einen Schnitt durch zwei komplementäre Verbundhalbschalen als Zwischenprodukte in einem Verfahren gemäß einem anderen Ausführungsbeispiel; und
• 7 einen Schnitt durch einen aus den Verbundhalbschalen nach 6 gebildeten Kraftstofftank.

Show it:

• 1 a section through a fuel tank, which is produced by a method according to the invention;
• 2 a section through a half-shell made of metal;
• 3 a section through a lower tool and the metal half-shell inserted therein;
• 4 the lower tool and the half-shell 3 together with an inner plastic half-shell molded into the metal half-shell by means of an upper tool;
• 5 a tool for forming metal and plastic blanks together according to another embodiment of the method;
• 6 a section through two complementary composite half-shells as intermediate products in a method according to another embodiment; and
• 7 a section through one of the composite half-shells 6 formed fuel tank.

the inside 1 The fuel tank shown has two complementary composite half-shells 10, 12, each of which is formed by an outer half-shell 14 made of stainless steel and an inner half-shell 16 made of plastic. The inner half-shells 16 are bonded to one another at their edges along a joint seam 18, so that together they form a closed inner tank. The outer half-shells 14 have flange-like edges, which are also connected to one another in a materially bonded manner along a joint seam 20, the joint seams 18 and 20 lying in a common plane and directly adjoining one another.

In at least one place, in the example shown on the seams, the walls of the tank have an opening 22 for a tank nozzle. Optionally, this breakthrough can also be located entirely within one of the two composite half-shells.

In this example, the two inner half-shells 16 form integrally formed baffles 24 for damping sloshing noises.

Also in this example, the outer half-shells 14 each have one or more small openings 26 through which some plastic material may flow during the molding of the inner half-shells 16 into a mold cavity 34 ( 3 ) leaked out on the outside of the outer half-shell. This plastic material forms an undercut 28, through which a fixed form-fitting toothing of metal and plastic is formed. In particular, this ensures that if there is a negative pressure in the tank, the inner half-shell 16 is not detached from the inner wall of the outer half-shell 14 due to the suction.

The essential steps of a method for producing the composite half-shells 10, 12 are in 2 until 4 shown.

In a first step, the half-shell 14 is made of stainless steel sheet by deep drawing or compression molding, as shown separately in 2 is shown. This half-shell is then how 3 shows inserted into a lower tool 30 of a mold. Before that, a recess 32 is formed in the edge of the half-shell 14, which later forms part of the opening 22. In addition, the openings 26 are drilled in the wall of the half-shell 14. The lower tool 30 forms the mold cavities 34 for the undercuts 28 at the locations of these openings. In this way, the sheet metal half-shell 14 becomes part of the lower tool 30, so to speak, and forms a mold cavity for molding the plastic half-shell 16.

4 12 shows the lower tool 30 and the half-shell 14 together with an upper tool 36 in a state during demolding of the inner half-shell 16 which has been formed in the mold by extrusion of a blank made of long-fiber-reinforced thermoplastic material. The upper tool 36 defines the inner contour of the plastic half-shell 16 and has mold cavities 38 for molding the baffles 24 . In the example shown, two of the baffles 24 and the associated mold cavities 38 are set at a slight angle to the demolding direction of the upper tool 36 . In that case, the plastic material of the half-shell 16 must have a certain flexibility so that the baffles can be removed from the mold. If this flexibility is not sufficient, an upper tool with core pulls can be used.

During extrusion, the thermoplastic material is heated to such an extent that it is sufficiently flowable and, after curing, adheres well to the inner wall of the outer metal half-shell 14 , so that the half-shells 14 and 16 together form the composite half-shell 12 . The other composite half-shell 10 of the in 1 The tank shown is made the same way.

Then the composite half-shells 10 and 12 are in the in 1 way shown edge-to-edge put together and connected by joining the. The edges of the inner half-shells 16 can be joined by thermal welding, ultrasonic welding or by gluing. The edges of the outer metal half-shells 14 can be joined at the same time or in a subsequent step by thermal welding, laser welding or else by gluing. In another embodiment, the edges of the half-shells 14 can also be joined by crimping.

5 Figure 11 illustrates a first step of an alternative method of making the composite half-shells. In this example, however, the inner half-shells 16 have no undercuts 28. A blank 40 made of the thermoplastic material and a stainless steel blank 42 are placed in a lower tool 30' and connected to an upper tool that corresponds to the upper tool 36 in 4 is similar, formed together to the outer half-shell 14 and the inner half-shell 16.

6 and 7 show composite half-shells 10', 12' or a complete tank according to another embodiment. The composite half-shells 10', 12' in this example each have a stamp 44 molded in one piece with the inner half-shell 16, which protrudes from the bottom of the composite half-shell and protrudes slightly beyond the plane of the rim of the composite half-shell. When joining the edges of the inner half shells 16 and the outer half shells 14 to form the complete tank according to 7 For example, the two stamps 44 are connected by ultrasonic welding to form a tie rod 44', which connects the opposite walls of the tank with high tensile strength, so that the tank can also withstand a high internal pressure without deforming.

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2014058331 A [0003]

Claims (8)

Process for the production of a fuel tank with nested shells made of plastic and metal, characterized by the following steps: - molding of two composite half-shells (10, 12; 10', 12'), each with an outer half-shell (14) made of metal and an inner half-shell ( 16) made of plastic, and - juxtaposing the two composite half-shells edge-to-edge and joining the edges of the inner half-shells (16) and the edges of the outer half-shells (14). procedure after claim 1 , in which, in the production of a composite half-shell (12), the outer half-shell (14) is formed from metal in a first step and the inner half-shell (16) is formed from plastic in a second step in a mold in which the outer half-shell ( 14) forms a wall of the mold cavity. procedure after claim 1 , in which, to produce a composite half-shell (12'), a blank (40) and a metal plate (42) are placed in a mold (30`) and shaped together to form the composite half-shell (12'). Method according to one of the preceding claims, in which a fiber-reinforced thermoplastic is used as the material for the inner half-shells (16). A method according to any one of the preceding claims, wherein internal baffles (24,44) of the tank are integrally molded with the inner half-shells (16). Method according to one of the preceding claims, in which the inner half-shells (16) and the outer half-shells (14) are interlocked with one another in a form-fitting manner by means of undercuts (28). Method according to one of the preceding claims, in which the edges of the inner half-shells (16) and the edges of the outer half-shells (14) are joined in one operation. Fuel tank for motor vehicles, with nested shells made of plastic and metal, characterized in that the tank is formed by two composite half-shells (10,12; 10', 12'), each having an inner half-shell (16) made of plastic, is tightly surrounded by an outer half-shell (14) made of metal, the inner half-shells (16) being connected to one another by a joint seam (18) and the outer half-shells (14) being connected to one another by a joint seam (20) which is the same as the joint seam (18 ) of the inner half-shells follows.

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