METHOD FOR MANUFACTURING AN INTERIOR UNIT FOR A MOTOR VEHICLE AND INTERIOR UNIT FOR A MOTOR VEHICLE AS WELL AS SCREW CONNECTION

Abstract

Method for manufacturing an interior unit (2) for a motor vehicle, comprising the steps: - Manufacturing a carrier (5) having a closed front (9) by injection molding, wherein a screw boss (8) is produced on a rear (10) of the carrier (5), the bore (11) of which is closed in the direction of the front (9) of the carrier (5) with a film-like carrier section (12) which has a reduced wall thickness (13) compared to the rest of the carrier; - Creating a foam layer (6) on the closed front (9) of the carrier (5).

Description

[0001] The invention relates to a method for producing an interior unit for a motor vehicle as well as an interior unit for a motor vehicle and a screw connection.

[0002] Interior components for motor vehicles, such as instrument panel supports, are increasingly being made of composite materials, particularly fiber-reinforced plastics, for reasons of weight reduction, among others. Such composite materials often feature a foamed middle layer, which, among other things, contributes to a particularly high-quality tactile impression in the vehicle interior.

[0003] Often, for example, add-on parts, such as trim strips or the like, are screwed onto instrument panel supports. To ensure reliable screw connections, so-called screw clips are often used. A screw clip is positioned near a hole in an instrument panel support, serving as a counterpart for a screw used to secure an add-on part to the instrument panel support. Attaching and using such screw clips is relatively complex and, among other things, negatively impacts assembly time and costs.

[0004] DE 37 37 230 A1 shows an injection-molded support with a screw boss. On the side of the support facing away from the screw boss, a cushioning layer made of plastic foam is arranged, which is covered by a film. A bore extends through the screw boss, the cushioning layer, and the film.

[0005] DE 11 2014 005 312 T5 shows an armrest upper part for a vehicle door. On the underside of the armrest upper part, a fastening lug is formed with a blind hole featuring an internal thread. A clamp can be attached to the underside of the armrest upper part using a screw. The screw is passed through a hole in the clamp and screwed into the blind hole.

[0006] EP 2 399 784 B1 discloses a method for attaching a cup holder base to a side panel of a motor vehicle using a self-tapping screw. The self-tapping screw is guided through a hole in the cup holder base and screwed through the side panel. As a result, a hole is created in the side panel.

[0007] DE 101 60 173 A1 shows a door panel consisting of a carrier part and a molded skin.

[0008] It is the object of the present invention to simplify the screwing of add-on parts to interior units made of composite materials.

[0009] This object is achieved by a method for producing an interior unit for a motor vehicle and by an interior unit for a motor vehicle having the features of the independent patent claims. Advantageous embodiments with expedient and non-trivial further developments of the invention are specified in the dependent claims.

[0010] In the method according to the invention for producing an interior unit for a motor vehicle, a carrier having a closed front side is produced by injection molding. A screw boss is produced on the rear side of the carrier, the bore of which is closed toward the front side of the carrier with a carrier section that has a reduced wall thickness compared to the rest of the carrier. Furthermore, a foam layer is produced on the closed front side of the carrier in the course of the method according to the invention.

[0011] The support having the screw boss is thus manufactured by injection molding, with a particularly important aspect of the invention being that the bore of the screw boss is sealed toward the front of the support during the injection molding process. This is achieved by the said support section sealing the bore toward the front of the support. Because the support section has a reduced wall thickness compared to the rest of the support, the support section can be severed or pierced particularly easily as soon as a screw needs to be screwed into the bore of the screw boss in order to screw an attachment to the interior unit.

[0012] Because the interior unit comprises both the carrier and the foam layer, it is important that the front of the carrier is closed during production. This ensures that no foam penetrates the carrier during the foaming process, i.e., during the production of the foam layer on the carrier. Since the bore of the screw boss toward the front of the carrier is closed with the carrier section, it can also be reliably ensured in the area of ​​the screw boss that no foam material penetrates the carrier during the production of the foam layer.

[0013] By providing the screw boss, which serves as a screw-in socket or screw tube for a screw, an add-on component can be screwed to the interior unit in a particularly simple and straightforward manner. The support section that closes the bore toward the front of the support forms a kind of film during the interior unit manufacturing process, through which no foam can penetrate during the production of the foam layer. However, this film-like support section can be relatively easily pierced with a screw as soon as an add-on component is to be screwed on after the interior unit has been completed. The screw clip mentioned above can therefore be omitted thanks to the method according to the invention, which also eliminates the work step of attaching or positioning the screw clip. Furthermore, waste can be avoided because the support section has a reduced wall thickness.

[0014] According to an advantageous embodiment of the invention, after the foam layer has been produced, the support section closing the bore of the screw dome is pierced using a punching tool. Preferably, further areas of the support are punched out during the punching process. If the interior unit being produced is, for example, an instrument panel support, a large number of recesses or through-openings must be created anyway, namely at the locations where certain components, such as displays, control elements and the like, are to be accommodated. The support section closing the bore of the screw dome can be punched out particularly easily because it has a reduced wall thickness.At the point where the support section is to be punched out in order to expose the hole in the screw boss towards the front, a die can be saved in the punching tool used. This is because the support section is so thin that it can be pierced without a die. Instead of piercing the support section using a punching tool, it is also possible, after the foam layer has been produced, to pierce the support section closing the hole in the screw boss using a screw. This screw is then screwed into the hole in the screw boss to attach an add-on part to the interior unit. In other words, it is also possible to simply pierce the support section closing the hole in the screw boss with the tip of a screw that is used anyway to attach an add-on part to the interior unit.Preferably, a self-tapping screw is used, which, when screwed into the cast core hole (i.e., the bore) of the support section, forms a counter-thread without cutting through a special thread geometry. Self-tapping screws therefore act as a positive locking device to prevent loss. When using a self-tapping screw, the process step of cutting the thread in the screw boss can be eliminated, resulting in additional time and cost savings.

[0015] A further advantageous embodiment of the invention provides for a decorative layer to be produced on a side of the foam layer facing away from the carrier. The interior unit is therefore preferably constructed from three different layers, namely the decorative layer and the carrier, with the foam layer being produced between the decorative layer and the carrier. The decorative layer is preferably pierced in an area of ​​the bore of the screw boss, so that a screw can be guided particularly easily through the decorative layer during the subsequent screwing process. The decorative layer is preferably pierced above the bore in the area of ​​the screw boss.

[0016] In a further advantageous embodiment of the invention, the decorative layer is produced by spray application or by powder sintering. In spray application, for example, a tool half is provided which replicates the contour of the decorative layer to be produced. The material from which the decorative layer is to be made is then applied to the tool using a spray head. This results in a particularly high degree of design freedom, so that a wide variety of shapes can be realized in a simple manner. In powder sintering, also known as powder slush or slush molding, the decorative layer is produced by primary molding. This also makes it possible to achieve a visually and haptically appealing surface because different grains, for example leather-like, can be introduced into a used tool.PVC or a thermoplastic elastomer based on urethane, olefin, or polyester can be used as the starting material. First, a mold is heated. Then, the heated mold is brought into contact with the plastic powder, which adheres to the mold wall and sinters. By rotating and pivoting the mold, a uniform thickness of the decorative layer is achieved. Excess powder can then be poured out. The adhering powder is then heated to completely gel it. Once the mold has cooled, the decorative layer can be removed. In contrast to the rotational molding process, this does not produce a hollow body, but rather a thick-walled film that has the shape of the mold.

[0017] A further advantageous embodiment of the invention provides for the carrier to be made of a fiber-reinforced thermoplastic. Long-fiber-reinforced polypropylene is preferably used. Compared to short-fiber-reinforced thermoplastics, long-fiber-reinforced thermoplastics have higher impact strength and their tendency to creep is also significantly lower, which favors their use in applications with increased quality requirements, such as in the automotive interior.

[0018] The foam layer is preferably made of polyurethane foam. The decorative layer can also be made of polyurethane, for example.

[0019] The interior unit according to the invention for a motor vehicle comprises a carrier having a closed front side and a screw boss on its rear side, the bore of which is closed toward the front side of the carrier with a film-like carrier section that has a reduced wall thickness compared to the rest of the carrier, with a foam layer attached to the closed front side. Advantageous embodiments of the method according to the invention are to be regarded as advantageous embodiments of the interior unit according to the invention, and vice versa.

[0020] The invention further relates to a screw connection which comprises the interior unit according to the invention and at least one attachment which is fastened to the interior unit by means of a screw screwed into the bore of the screw dome.

[0021] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures alone, can be used not only in the specified combination but also in other combinations or on their own, without departing from the scope of the invention.

[0022] The drawing shows: Fig. 1 is a schematic side sectional view of a screw connection comprising an interior unit to which an attachment is screwed, the interior unit comprising a carrier, a foam layer and a decorative layer; Fig. 2 is a schematic side sectional view showing only the interior unit, which comprises the decorative layer, the foam layer and the support, with a screw dome formed on the underside thereof; and in Fig. 3 an enlarged sectional view in the area of ​​the screw dome, which has a bore that is closed in the direction of the foam layer by a carrier section.

[0023] A screw connection 1 is shown in a schematic side sectional view in Fig. 1. The screw connection 1 comprises an interior unit 2 and an attachment 3, which is fastened to the interior unit 2 by means of a screw 4. The interior unit 2 has a multi-layer structure. The interior unit 2 comprises an injection-molded carrier 5, a foam layer 6, and a decorative layer 7. The carrier 5 also has a screw dome 8, which serves as a screw-in socket or screw tube for the screw 4, by means of which the attachment 3 is screwed to the interior unit 2.

[0024] The interior unit 2 can be, for example, an instrument panel support, and the attachment 3 can be, for example, a decorative strip screwed to the instrument panel support. The side of the decorative layer 7 facing away from the foam layer 6 forms the visible side, which can be seen by vehicle occupants. The provision of the integrated screw boss 8 allows the attachment 3 to be attached to the interior unit 2 particularly easily.

[0025] In Fig. 2, the interior unit 2 is shown alone in a schematic side sectional view. As already mentioned, the carrier 5 is manufactured by injection molding, preferably from a long-fiber-reinforced polypropylene. The carrier 5 is produced with a closed front side 9, with the screw boss 8 being produced as an integral component of the carrier 5 on a rear side 10 of the carrier 5 during the injection molding process. A bore 11 of the screw boss 8 is preferably produced directly during the injection molding process.

[0026] In Fig. 3 is the Fig. 2 is shown in an enlarged sectional view. During the production of the carrier 5 by injection molding, the bore 11 of the screw dome 8 is closed in the direction of the front side 9 with a carrier section 12, which has a significantly reduced wall thickness 13 compared to the rest of the carrier 5. The entire front side 9 of the carrier 5 produced by injection molding therefore has no through openings whatsoever. This is important so that during the further production of the interior unit 2, the foam material from which the foam layer 6 is made does not press through the carrier 5.

[0027] The decorative layer 7 can be produced, for example, by spray application or by powder sintering. For example, the decorative layer 7 is inserted into a lower tool (not shown here), after which the foam layer 6 is applied to the decorative layer 7. The carrier 5 is received in an upper tool (also not shown here), with the upper tool and lower tool subsequently being moved together. This produces a closed skin-foam carrier in the form of the interior unit 2.

[0028] After the interior unit 2 has been manufactured, the support section 12 closing the bore 11 of the screw boss 8 can be pierced, for example, using a punching tool. Alternatively, it is also possible to leave the support section 12 intact. Preferably, the decorative layer 7 is pierced in an area located above the bore 11 of the screw boss 8. This allows the screw 4 to be inserted more easily through the decorative layer 7 later. Furthermore, it is easily recognizable where the screw 4 must be inserted into the decorative layer 7.

[0029] The decorative layer 7 can, for example, have a thickness of 1.5 mm, wherein the carrier section 12, which closes the bore 11, can, for example, have a thickness of only 0.2 mm.

[0030] To Fig.To produce the screw connection 1 shown in Figure 1, the screw 4 simply needs to be inserted through the pre-punched decorative layer 7 above the bore 11 of the screw boss 8. The foam layer 6 can be penetrated relatively easily by means of the screw 4. The same applies to the support section 12, since this has the aforementioned very thin wall thickness 13. The screw 4 is preferably a self-tapping screw, so that it automatically forms a thread in the bore 11 of the screw boss 8. A separate manufacturing step for threading the bore 11 of the screw boss 8 can therefore be omitted. Due to the provision of the screw boss 8, the add-on part 3 can therefore be attached to the interior unit 2 particularly easily and quickly using the screw 4. LIST OF REFERENCE SYMBOLS 1 screw connection 2 interior units 3 Attachment 4 screw 5 carriers 6 foam layer 7 decorative layer 8 screw dome 9 Front 10 Back 11 Hole 12 support section 13 Wall thickness B area

Claims

[1] Method for producing an interior unit (2) for a motor vehicle, comprising the steps: - producing a support (5) having a closed front side (9) by means of injection molding, wherein a screw dome (8) is produced on a rear side (10) of the support (5), the bore (11) of which is closed in the direction of the front side (9) of the support (5) with a film-like support section (12) which has a reduced wall thickness (13) compared to the rest of the support; - Producing a foam layer (6) on the closed front (9) of the carrier (5). [2] Method according to claim 1, characterized by that after the foam layer (6) has been produced, the support section (12) closing the bore (11) of the screw dome (8) is pierced by means of a punching tool. [3] Method according to one of claims 1 or 2, characterized bythat a decorative layer (7) is produced on a side of the foam layer (6) facing away from the carrier (5). [4] Method according to claim 3, characterized by that the decorative layer (7) is pierced in an area of ​​the bore (11) of the screw dome (8). [5] Method according to one of claims 3 or 4, characterized by that the decorative layer (7) is produced by spray application or by powder sintering. [6] Method according to one of the preceding claims characterized by that the carrier (5) is made of a fiber-reinforced thermoplastic material. [7] Method according to one of the preceding claims characterized by that the foam layer (6) is made of polyurethane foam. [8] Method according to one of claims 3 to 5 characterized by that the decorative layer (7) is made of polyurethane. [9] Interior unit (2) for a motor vehicle, comprising a support (5) having a closed front side (9) and having a screw dome (8) on its rear side (10), the bore (11) of which is closed in the direction of the front side (9) of the support (5) with a film-like support section (12) which has a reduced wall thickness (13) compared to the rest of the support (5), a foam layer (6) being attached to the closed front side (9). [10] Screw connection (1), comprising an interior unit (2) according to claim 9 and at least one attachment part (3) which is fastened to the interior unit (2) by means of a screw (4) screwed into the bore (11) of the screw dome (8).

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