DE102017103293B4 - METHOD OF MANUFACTURING AN INJECTION MOLDED COMPONENT FOR AN AUTOMOTIVE VEHICLE AND INJECTION MOLDED COMPONENT FOR AN AUTOMOTIVE VEHICLE - Google Patents

Abstract

Method for producing an injection molded component (1) for a motor vehicle, in which a plastic melt interspersed with reinforcing fibers (7) is injected into a shaping cavity (12) of an injection molding tool (9) and a linear mechanical weakening (3, 8) in one serves as an airbag cover Area (2) of the injection molded component (1) is produced, characterized in that the linear mechanical weakening (3, 8) is produced in that at least one locking slide (13) of the injection molding tool (9) is moved transversely to a flow direction (6) of the plastic melt in the shaping cavity (12) of the injection molding tool (9) is arranged so that when the plastic melt hits the locking slide (13), the reinforcing fibers (7) are aligned parallel to the locking slide (13).

Description

The present invention relates to a method for producing an injection-molded component for a motor vehicle and an injection-molded component for a motor vehicle of the type specified in the preambles of the independent patent claims.

On the passenger side of motor vehicles there is usually a passenger airbag under what is known as the instrument panel support. When the front passenger airbag is triggered, this instrument panel support must release an opening for the airbag bag with a defined force that is as constant as possible. At the same time, however, this area must not be weakened so much that it does not break when misused. Fluctuations in the manufacturing process can affect these forces. In addition, great importance is usually attached to the optical homogeneity of the surface in the area of the instrument panel on the passenger side, so that the airbag area should not be visible as such.

the DE 102 07 705 B4 shows a vehicle interior panel for concealing an airbag. This vehicle interior paneling is produced by injection molding from a plastic melt interspersed with reinforcing fibers. In order to realize a kind of predetermined breaking point or predetermined breaking line above the airbag to be accommodated in the vehicle interior paneling, provision is made for the vehicle interior paneling to be made from two different materials. The area directly above the airbag is made from a different material than the rest of the vehicle's interior trim.

the DE 10 2013 215 023 A1 shows a carrier component for a motor vehicle, which is produced by means of injection molding. The carrier component has a jagged edge area.

the U.S. 2006/0237952 A1 shows a method for manufacturing an airbag cover. In order to produce a predetermined breaking line, provision is made for first arranging a slide in a type of closed position within a cavity of an injection molding tool. While the injection mold is being filled, this slide is pulled out of the shaping cavity of the injection mold.

the DE 102 34 198 A1 shows a method for producing an interior component for a motor vehicle, which has a covering area for an airbag. The interior component is manufactured using injection molding. A perforation serving as a breaking line is embossed in the covering area by means of a stamp. A casting material is first introduced into a cavity of a tool. Even before the cast material has completely solidified, the stamp is extended into the cavity, as a result of which projections arranged on the stamp dip into the cast material and as a result the fracture line is produced. The ram is only retracted again when the casting material can no longer flow back into the respective holes produced in the fracture line.

the DE 10 2015 203 964 A1 describes an impact body for a passenger airbag, the impact body having a flap for the passenger airbag.

It is the object of the present invention to provide a method for producing an injection-molded component for a motor vehicle and an injection-molded component for a motor vehicle, by means of which defined tearing open of an airbag cover on the injection-molded component is promoted.

This object is achieved by a method for producing an injection-molded component for a motor vehicle and by an injection-molded component for a motor vehicle with the features of the independent patent claims. Advantageous configurations with expedient and non-trivial developments of the invention are specified in the claims.

In the method according to the invention for producing an injection molded component for a motor vehicle, a plastic melt interspersed with reinforcing fibers is injected into a shaping cavity of an injection mold. A linear mechanical weakening is produced in an area of the injection-molded component that serves as an airbag cover. The method according to the invention is characterized in that the linear mechanical weakening is produced by arranging at least one blocking slide of the injection molding tool transversely to a flow direction of the plastic melt in the shaping cavity of the injection molding tool, so that when the plastic melt hits the blocking slide, the reinforcing fibers are parallel to the blocking slide relay a message. The locking slide can be actuated mechanically, hydraulically or electrically, for example.

The linear mechanical weakening acts as a type of predetermined breaking point or tearing edge, along which the area of the injection-molded component that serves as an airbag cover can tear open when an airbag is triggered. The direction of movement in which the locking slide can be moved into and out of the shaping cavity of the injection mold runs transversely to said flow direction of the plastic melt. Below the direction of flow is the direction of flow ment of the plastic melt interspersed with the reinforcing fibers around the area of the shaping cavity of the injection mold into which the locking slide can be moved.

As a rule, the reinforcing fibers of the plastic melt are aligned parallel to the flow direction of the plastic melt. In the free melt flow, the reinforcing fibers of the plastic melt behave in a similar way to tree trunks that swim with the flow of a river. Because the locking slide is arranged transversely to the flow direction of the plastic melt in the shaping cavity of the injection mold, the reinforcing fibers of the plastic melt striking the locking slide are aligned parallel to the locking slide. The orientation of the locking slide transversely to the direction of flow of the plastic melt is to be understood as meaning that a surface of the locking slide that stands in the way of the plastic melt is aligned transversely to the direction of flow of the plastic melt.

The locking slide thus defines a kind of end of the flow path for the plastic melt mixed with the reinforcing fibers, as a result of which the reinforcing fibers are arranged transversely to the flow front of the melt and thus parallel to the locking slide. By means of the locking slide, at least one flow front of the plastic melt interspersed with the reinforcing fibers is influenced in terms of its flow properties and direction.

By means of the method according to the invention it can be ensured that no or at least virtually no reinforcing fibers of the plastic melt lie over the linear mechanical weakening. Instead, the use of the locking slide according to the invention ensures that the reinforcing fibers are aligned parallel to the linear mechanical weakening. The linear mechanical weakening is thus achieved in that the reinforcing fibers are aligned parallel to the linear mechanical weakening in the area of the linear mechanical weakening. This defines a type of tear line along which the airbag cover can tear open in a defined manner. When the airbag cover tears open, the tearing runs parallel to the reinforcement fibers.

The mechanical weakening does not necessarily mean a reduction in cross section. On the contrary, the linear mechanical weakening preferably has the same thickness as the rest of the injection-molded component.

The mechanical material weakening, ie the linear mechanical weakening, is thus achieved in the method according to the invention by the specific arrangement of the reinforcing fibers during the injection molding process. The injection-molded component produced using the method according to the invention therefore does not have to be subjected to any subsequent processes, such as reducing the material thickness using a laser, in order to produce the linear mechanical weakening.

An advantageous embodiment of the invention provides that an H-shaped mechanical weakening is produced in the area of the airbag cover of the injection molded component. In principle, this H-shaped mechanical weakening works like two flaps that can swing open as soon as the relevant airbag is triggered.

Such an H-shaped mechanical weakening is particularly advantageous in sports cars when there is relatively little space between the instrument panel support and the windshield.

According to an alternative advantageous embodiment of the invention, it is provided that a U-shaped mechanical weakening is produced in the area of the airbag cover of the injection molded component. This U-shaped mechanical weakening in the area of the airbag cover works like a single flap that can swing open as soon as the relevant airbag is deployed. Such a U-shaped mechanical weakening has a geometrically simpler structure than the H-shaped mechanical weakening. Such U-shaped mechanical weakenings can be used in particular in vehicles in which there is a relatively large amount of space between the instrument panel support and the windshield.

In a further advantageous embodiment of the invention, it is provided that the injection-molded component is produced by one-component injection molding. It is therefore only a single plastic component, which is interspersed with the reinforcing fibers, required to produce the injection molded component. This makes the injection molding process particularly easy and fast.

According to a further advantageous embodiment of the invention, it is provided that after the plastic melt hits the at least one locking slide, the latter is withdrawn from the cavity while the plastic melt is still being injected, so that further plastic melt continues to flow in the area of the linear mechanical weakening. For example, flows first - so long as the locking slide is in its in the shaping cavity is arranged protruding blocking position, the plastic melt from an injection point of the injection mold in said flow direction only up to the locking slide. After the locking slide has been pulled out, further plastic melt then flows, for example, from a further injection point of the injection molding tool to the area where the locking slide had previously blocked the flow path of the plastic melt. So after the reinforcing fibers of the plastic melt have been aligned parallel to the locking slide, the locking slide is pulled out of the shaping cavity, ie the cavity, of the injection molding tool. The at least one locking slide, which has the same width as the linear mechanical weakening, initially encapsulates the area of the injection-molded component that serves as an airbag cover for filling with the plastic melt interspersed with reinforcing fibers. By pulling the locking slide, more plastic melt can then flow. In the area of the injection-molded component serving as an airbag cover, it can also be ensured with the linear mechanical weakening that the injection-molded component has at least essentially the same material thickness in the area of the linear mechanical weakening as in the rest of the injection-molded component. The area of the injection-moulded component that serves as the airbag cover, together with the line-shaped mechanical weakening, is manufactured so that it is invisible or virtually invisible from the outside.

A further advantageous embodiment of the invention provides that the plastic melt interspersed with reinforcing fibers is produced from a long-fiber-reinforced thermoplastic. One speaks of a fiber-reinforced thermoplastic when the reinforcing fibers, which can be glass fibers, carbon fibers or aramid fibers, for example, have a length of at least several millimeters in the finished component. The reinforcing fibers preferably have a length of up to a maximum of 11 millimeters. Compared to short-fiber-reinforced thermoplastics, long-fiber-reinforced thermoplastics have a higher impact strength and their tendency to creep is significantly lower, which favors this type of fiber composite materials and their use with increased quality requirements, such as in the interior of the automotive industry.

The injection molded part according to the invention for a motor vehicle is made from a plastic interspersed with reinforcing fibers and has at least one linear mechanical weakening in an area serving as an airbag cover. The injection-molded component according to the invention is characterized in that the linear weakening is formed by reinforcing fibers aligned parallel to the linear weakening. Due to the fact that the reinforcing fibers are formed parallel to the linear weakening, none of the reinforcing fibers projects beyond the linear weakening. For example, the reinforcing fibers are aligned transversely to the main direction of extent of the linear weakening in a range of one millimeter parallel to the main direction of extent of the linear weakening. As a result, the tearing open of the airbag cover itself is promoted on the one hand. On the other hand, this also prevents uncontrolled propagation of cracks on the airbag cover when an airbag is deployed. This is because the reinforcing fibers, which are aligned parallel to the main extension direction of the linear weakening in the area of the linear weakening, prevent or at least make it more difficult for cracks to grow transversely to the actually desired tearing direction of the airbag cover. A particularly defined tearing process is thus ensured when an airbag is triggered in the area serving as an airbag cover along the linear mechanical weakening.

The injection-molded component is preferably an instrument panel support, with the airbag cover preferably being designed to cover a passenger airbag. However, the injection-molded component can also be other components than an instrument panel support, in which case the airbag cover can also be used to cover other airbags.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawing.

• 1 eine ausschnittsweise und schematische Darstellung eines aus einem faserverstärkten Kunststoff hergestellten Instrumententafelträgers, welcher in einem als Airbagabdeckung dienenden Bereich eine H-förmige mechanische Schwächung aufweist;
• 2 eine vergrößerte Detailansicht des Instrumententafelträgers, wobei die Ausrichtung von Verstärkungsfasern im Bereich der H-förmigen mechanischen Schwächung dargestellt sind;
• 3 eine schematische und ausschnittsweise Darstellung einer weiteren Ausführungsform des Instrumententafelträgers, welcher ebenfalls aus einem faserverstärkten Kunststoff hergestellt ist, wobei in einem als Airbagabdeckung dienenden Bereich eine U-förmige mechanische Schwächung vorgesehen ist;
• 4 eine vergrößerte Detailansicht, in welcher ein Ausschnitt der H-förmigen mechanischen Schwächung und die Ausrichtung von Verstärkungsfasern in diesem Bereich dargestellt ist; und
• 5 eine schematische Darstellung eines Spritzgusswerkzeugs, mittels welchem die Instrumententafelträger herstellbar sind, wobei die Positionierung eines Sperrschiebers zu Beginn und zum Ende des Spritzgussvorgangs schematisch dargestellt ist.

The drawing shows in:

• 1 a sectional and schematic representation of a dashboard support made of a fiber-reinforced plastic, which has an H-shaped mechanical weakening in an area serving as an airbag cover;
• 2 an enlarged detail view of the dashboard support, wherein the alignment of reinforcing fibers in the area of the H-shaped mechanical weakening are shown;
• 3 a schematic representation of a detail of a further embodiment of the instrument panel support, which is also made of a fiber-reinforced plastic, with a U-shaped mechanical weakening being provided in an area serving as an airbag cover;
• 4 an enlarged detail view in which a section of the H-shaped mechanical weakening and the alignment of reinforcing fibers in this area is shown; and
• 5 a schematic representation of an injection molding tool, by means of which the dashboard support can be produced, wherein the positioning of a locking slide at the beginning and at the end of the injection molding process is shown schematically.

Elements that are the same or have the same function have been provided with the same reference symbols in the figures.

A dashboard support 1 for a motor vehicle is shown in detail and schematically in 1 shown. A region 2 of the instrument panel support 1 serving as an airbag cover has an H-shaped mechanical weakening 3 . Two flaps 4 are formed by this H-shaped mechanical weakening 3 . As soon as a passenger airbag is deployed under area 2 serving as an airbag cover, the two flaps 4 can swing open in opposite directions, so that the airbag sack can unfold and step out of area 2 . The H-shaped mechanical weakening 3 is therefore a type of linear mechanical weakening of the instrument panel support 1.

In 2 is the in 1 marked area 5 shown in an enlarged view. A flow direction 6 of a plastic melt interspersed with reinforcing fibers 7 is indicated schematically by the arrow. The instrument panel support 1 is made by injection molding. How based on 2 As can be seen, the reinforcement fibers 7 in the region of the H-shaped mechanical weakening 3 are aligned essentially parallel to the respective legs of the H-shaped mechanical weakening 3 . As a result, if necessary, ie when the airbag is deployed, the H-shaped mechanical weakening 3 can tear particularly well, since none of the reinforcing fibers 7 protrude beyond the respective lines of the H-shaped mechanical weakening 3 .

In 3 a further embodiment of the instrument panel support 1 is partially shown in a schematic representation. The area 2 serving as an airbag cover has a U-shaped mechanical weakening 8 in this embodiment. This defines a single flap 4, which can pivot upwards when the airbag is triggered.

In 4 is the in 3 marked area 5 shown in an enlarged view. Again, a flow direction 6 of the plastic melt interspersed with reinforcing fibers 7 is shown. Along the U-shaped mechanical weakening 8 the reinforcing fibers 7 are in turn aligned parallel to the U-shaped mechanical weakening 8 so that a defined tearing of the flap 4 along the U-shaped mechanical weakening 8 is promoted. The reinforcement fibers 7 are therefore aligned in such a way that they do not pass over the U-shaped mechanical weakening 8 .

In 5 an injection molding tool 9 is shown, by means of which the instrument panel support 1 can be produced. The injection mold 9 has a stationary mold half 10 and a movable mold half 11 . The fixed tool half 10 forms the so-called nozzle side of the injection molding tool 9. In the fixed tool half 10, several injection points (not shown here) can be provided through which the plastic melt interspersed with the reinforcing fibers 7 can be injected.

The fixed tool half 10 and the movable tool half 11 enclose a shaping cavity 12 which defines the shape of the instrument panel support 1 . In addition, the injection molding tool 9 has an electrically, hydraulically or mechanically controllable and movable blocking slide 13 which can be moved into and out of the shaping cavity 12 .

In the illustration on the left of the injection mold 9, the positioning of the locking slide 13 is shown at the beginning of the injection molding process, with the positioning of the locking slide 13 being shown at the end of the injection molding process in the right illustration. Depending on whether the H-shaped mechanical weakening 3 or the U-shaped mechanical weakening 8 is to be produced, the blocking slide 13 has a corresponding shape. To produce the H-shaped mechanical weakening 3, the locking slide 13 preferably also has an H-shape. On the other hand, if the U-shaped mechanical weakening 8 is to be produced, the blocking slide 13 preferably has a U-shape. The locking slide 13 can be designed in one piece or composed of several parts.

At the start of the injection molding process, the locking slide 13 is moved relatively far into the shaping cavity 12, as in the left-hand illustration in FIG 5 shown. If the instrument panel support 1, for example, have a wall thickness of 2 to 4 millimeters, the position remains nization of the locking slide 13 initially only a remaining wall thickness of, for example, 0 to 2 millimeters. By moving the blocking slide 13 into the shaping cavity 12, the linear mechanical weakening is produced in the area 2 serving as the airbag cover, since the blocking slide 13 is arranged transversely to the flow direction 6 of the plastic melt permeated with the reinforcing fibers 7 in the shaping cavity 12 of the injection molding tool 9.

When the plastic melt impinges on the locking slide 13 , the reinforcing fibers 7 are thereby aligned parallel to the locking slide 13 . Towards the end of the injection molding process, the locking slide 13 is retracted, preferably up to the maximum base wall thickness of the rest of the instrument panel support 1. The locking slide 13 is therefore preferably completely retracted or pulled out of the shaping cavity 12.

First of all, the plastic filling is encapsulated by the positioning of the locking slide 13 within the shaping cavity 12, with further plastic melt being able to flow by pulling out the locking slide 13. As a result, the reinforcing fibers 7 are initially aligned parallel to the linear mechanical weakening, ie either the H-shaped mechanical weakening 3 or the U-shaped mechanical weakening 8 . By subsequently pulling out the locking slide 13, it can be ensured that the instrument panel support 1 produced by injection molding has the same wall thickness as the rest of the instrument panel support 1 everywhere, i.e. also in the area of the H-shaped mechanical weakening 3 or the U-shaped mechanical weakening 8.

Reference List

1

instrument panel support

2

Area

3

H-shaped mechanical weakness

4

flap

5

Area

6

flow direction

7

reinforcement fiber

8th

U-shaped mechanical weakening

9

injection molding tool

10

fixed tool half

11

movable tool half

12

shaping cavity

13

locking slide

Claims (9)

Method for producing an injection molded component (1) for a motor vehicle, in which a plastic melt interspersed with reinforcing fibers (7) is injected into a shaping cavity (12) of an injection molding tool (9) and a linear mechanical weakening (3, 8) in one serves as an airbag cover Area (2) of the injection-molded component (1), characterized in that the linear mechanical weakening (3, 8) is produced by moving at least one locking slide (13) of the injection-molding tool (9) transversely to a flow direction (6) of the plastic melt in the shaping cavity (12) of the injection molding tool (9) is arranged so that when the plastic melt hits the locking slide (13), the reinforcing fibers (7) are aligned parallel to the locking slide (13). procedure after claim 1 , characterized in that an H-shaped mechanical weakening (3) in the area (2) of the airbag cover of the injection molded component (1) is produced. procedure after claim 1 , characterized in that a U-shaped mechanical weakening (8) in the area (2) of the airbag cover of the injection molded component (1) is produced. Method according to one of the preceding claims, characterized in that the injection molded component (1) is produced by one-component injection moulding. Method according to one of the preceding claims, characterized in that after the plastic melt hits the at least one locking slide (13), the latter is withdrawn from the cavity (12) while the plastic melt is still being injected, so that in the region of the linear mechanical weakening (3, 8) further plastic melt continues to flow. Method according to one of the preceding claims, characterized in that the plastic melt interspersed with reinforcing fibers (7) is produced from a long-fibre-reinforced thermoplastic. Injection molded component (1) for a motor vehicle, which is made from a plastic interspersed with reinforcing fibers (7) and has at least one linear mechanical weakening (3, 8) in an area (2) serving as an airbag cover, characterized in that the linear weakening ( 3, 8) through reinforcement fibers (7) aligned parallel to the linear weakening (3, 8). Injection molded component (1) after claim 7 , characterized in that the injection molded component (1) is an instrument panel support (1). Injection molded component (1) after claim 7 or 8th , characterized in that the airbag cover is designed to cover a passenger airbag.

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