Patent Publication Number: US-2022234521-A1

Title: Vehicle interior panel and method of manufacturing same

Description:
TECHNICAL FIELD 
     The present disclosure is related generally to vehicle interiors and, more particularly, to instrument panels and other vehicle interior panels having a substrate, foam layer, and decorative layer. 
     BACKGROUND 
     Weight reduction in vehicles is a common goal in the automotive industry. Accordingly, decreasing the thickness of more rigid parts such as substrates in vehicle interior panels can help reduce weight. However, reducing the thickness of the substrate can result in undesirable warpage when the panel is formed, foamed, or molded. JP 2009208574 to Yasushi addresses thermal warpage of an installed instrument panel, but does not contemplate the issue of creating a thin-walled substrate that is more susceptible to deflection during manufacture in particular. 
     SUMMARY 
     An illustrative vehicle interior panel such as an instrument panel includes a substrate having a thickness between 0.5 mm and 2.25 mm, inclusive, a decorative layer, and an intermediate layer located between the substrate and the decorative layer. A post-form warpage of the substrate is less than 15 mm at an edge region of the substrate. 
     In various embodiments, the edge region is a windshield edge and the post-form warpage is in a Z direction. 
     In various embodiments, a serpentine rib located near the windshield edge. 
     In various embodiments, an extension flange is located at least partially between the windshield edge and the serpentine rib. 
     In various embodiments, the extension flange extends out from the windshield edge in an X direction and the serpentine rib projects from the extension flange in the Z direction. 
     In various embodiments, the serpentine rib is located along a majority of a distal edge of the extension flange. 
     In various embodiments, the windshield edge has a primary arc, the extension flange has a primary arc, and the serpentine rib has a primary arc, and each primary arc is configured to match a contour of a windshield. 
     In various embodiments, the serpentine rib includes a plurality of undulations. 
     In various embodiments, each undulation has a peak and the peak is an angle between 30° and 60°, inclusive. 
     In various embodiments, the plurality of undulations includes more than 20 undulations. 
     In various embodiments, each undulation has an amplitude and a wavelength, and a ratio of the amplitude to the wavelength is between 1:6 and 1:2, inclusive. 
     In various embodiments, there is a method of manufacturing the vehicle interior panel, comprising the steps of molding the substrate and foaming a foam layer between the decorative layer and the substrate to form the intermediate layer. 
     In various embodiments, the substrate is molded with a serpentine rib. 
     In various embodiments, the serpentine rib is located on an extension flange. 
     In various embodiments, the method includes the step of removing the serpentine rib and the extension flange after the foaming step. 
     It is contemplated that any number of the individual features or steps of the above-described embodiments and of any other embodiments depicted in the drawings or description below can be combined in any combination to define an invention, except where features or steps are incompatible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a perspective view of the interior of a vehicle passenger cabin showing example vehicle interior panels, such as an instrument panel; 
         FIG. 2  is a cross-sectional view of a portion of the instrument panel of  FIG. 1 ; 
         FIG. 3  is a computer-aided engineering (CAE) model of a prior art substrate; 
         FIG. 4  is a CAE model of an embodiment of a substrate for the instrument panel depicted in the figures and described herein; 
         FIG. 5  is side view of the substrate of  FIGS. 1, 2, and 4 , showing its serpentine rib; 
         FIG. 6  a top view of the substrate of  FIGS. 1.2, 4, and 5 ; and 
         FIG. 7  is an enlarged view of a portion of the serpentine rib of  FIGS. 1, 2, and 4-6 . 
     
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Described herein is a vehicle interior panel that is particularly configured to reduce manufacture-related warpage in thin-walled substrates. Typical substrate thicknesses for vehicle interior panels are between 2.5 and 4 mm. Thin-walled substrates are about 2.0 mm, or between about 0.5-2.25 mm. The thin-walled substrates help promote vehicle weight reduction. However, these thin-walled structures are more susceptible to warpage during manufacture. For example, when subjected to a foaming process to introduce a foam layer between the substrate and a decorative layer, a certain degree of post-form warpage can be present. With thin-walled substrates that are between 0.5-2.25 mm in particular, the degree of post-form warpage can make the part unsuitable for installation and/or performance in the vehicle. This post-form warpage is present before the panel is installed in the vehicle, and thus is different than thermal warpage that may occur after installation. With substrates that fall into the standard thickness range between 2.5 and 4 mm, the post-form warpage amount does not make the part unsuitable. The panels and manufacturing methods described herein strategically minimize the amount of post-form warpage in a thin-walled substrate by including a serpentine rib to help structurally support and improve the rigidity of the substrate body during manufacture. 
       FIG. 1  is a perspective view of an interior of a passenger cabin  10  of a vehicle  12  having an interior panel  14  that is manufactured in accordance with the methodology described below. The interior panel  14  is an instrument panel  16 . As will be detailed further, warpage along a windshield edge  18  of the instrument panel  16  can be particularly problematic, especially with thin-walled substrates. However, the structures and methods disclosed herein may be used in the manufacture of other interior panels, such as one or more panels for the center console  20 , armrest  22 , door panel  24 , or one or more storage compartments  26 , to cite a few examples. Accordingly, while the discussion below is focused on the instrument panel  16  implementation, the teachings may also be applicable to other vehicle interior panels. 
       FIG. 2  is a cross-sectional, schematic view of a portion of an embodiment of the vehicle interior panel  14 , or more particularly, the instrument panel  16 . The vehicle interior panel  14  includes a decorative layer  28 , a substrate  30 , and an intermediate or foam layer  32  between the decorative layer and the substrate. Adhesive or bonding layers can be included between two or more of the various layers or components of the interior panel  14 . Further, other layers may be included in addition to those particularly described, such as one or more protective outer layers, fabric interlayers, conductive electronic layers, or other functional and/or aesthetic layers. 
     The decorative layer  28  has a decorative side  34 , which is the side of the panel  14  lining the interior of the passenger cabin  10  when installed in the vehicle  12 . The decorative layer  28  can be a single layer, or it may have a multi-layer structure (e.g., a wood sheet complex having a fabric interlayer and one or more protective outer layers). Other materials for the decorative layer are certainly possible, such as fiber-containing resins, leather, or a polymer skin layer, to cite a few examples. When a resin component is included in the decorative layer, it may be colored or tinted for additional contrast or visual interest. The decorative layer  28  may have a thickness in a range from 0.5 mm to 2.5 mm, or preferably from 0.5 mm to 1.5 mm. In one example, the thickness of the decorative layer  28  is between 0.6 mm and 1.0 mm, or about 0.8 mm. Other thickness ranges and configurations are certainly possible. For example, the decorative layer  28  may be thicker in certain regions than others, or it may have a curved or non-planar shape. 
     The substrate  30  is semi-rigid and generally defines the overall shape and structure of the panel  14 . An example of a suitable semi-rigid construction is injection molded glass-reinforced polypropylene having a wall thickness T in a range from 0.5 to 2.25 mm. This thin-walled structure is distinguishable from typical substrates having a thickness in the range of 2.5 mm to 4.0 mm (standard-walled). Without the structural modifications described herein, the thin-walled structures falling into the range of 0.5 to 2.25 mm can suffer from a high degree of post-form warpage, which can be particularly detrimental in larger panels, such as the instrument panel  16 . Along longer edges, such as the windshield edge  18 , this post-form warpage can be even more pronounced in the thin-walled structures. Minimizing this post-form warpage can result in a more structurally sound thin-walled substrate  30 . The post-form warpage may be a result of the injection molding process, which causes internal stress in the substrate  30 . If, for example, there is post-form warpage that varies the shape of the substrate  30  from the nominal CAD model, sometimes, putting the substrate on the foaming tool lid will help bring the part back to nominal. However, after the part is foamed, the injected substrate  30  has memory and will warp back to its original state. 
     While injection molded plastic is a preferred material for the substrate  30 , other materials and combinations of materials exhibiting similar shape-maintaining characteristics may be used. The substrate  30  is described as semi-rigid to distinguish from perfectly rigid (i.e., entirely inflexible), but should be sufficiently rigid to support its own weight and the weight of the decorative layer  28  and the intermediate or foam layer  32 , along with any other attached components, without noticeable sagging or bending. The substrate  30  should be able to endure severe temperature extremes without changing shape, and should not exhibit brittle fractures in vehicle collision scenarios. In some embodiments, the panel  14  is a relatively small subpanel of a larger interior panel, in which case, an unreinforced plastic material can be used for the substrate  30 . The illustrated substrate  30  also includes reference positioners  36  on the outer side  38  used to position and fix the substrate and any attached layers or components in a repeatable location during manufacture. The outer side  38  generally faces away from the interior cabin  10  of the vehicle  12 , while the inner side  40  generally faces toward the interior cabin. The reference positioners  36  on the outer side  38  illustrated in  FIG. 2  are but one example of suitable positioners. The substrate  30  may also include one or more substrate openings for the insertion of foam material for the foam layer  32 . 
     The intermediate layer  32  is advantageously a foam layer that can assist the decorative layer  28  in providing desired tactile characteristics to the panel  14  in the form of elastic cushioning that compresses when a force is applied to the outer decorative side  34  of the panel  14  and decompresses when the force is removed to return the decorative layer to its original position. The foam layer  32  can also provide sound deadening and/or have a non-uniform thickness to fill space between the decorative layer  28  and the substrate  30  when the respective contours of the decorative layer and substrate are different from each other. In the illustrated example, the foam layer  32  is a backfilled or a closed pour, foam-in-place material layer formed by introducing a foam material, such as a liquid foam precursor, into a space between the decorative layer  28  and the substrate  30 , with at least the decorative layer constrained in the desired final shape in a foam molding tool. The foam material expands to fill and take the shape of the space and cures to form the foam layer  32 . One suitable foam layer material is polyurethane foam formed from a liquid precursor material comprising a polyol and a diisocyanate. Other foam materials (e.g., polyolefin-based) are possible, as are other foaming processes (e.g., use of a heat-activated foaming agent). The foam layer  32  may range in thickness from 1 mm to 10 mm, can be separately provided and adhered with adjacent material layers. In other embodiments, the intermediate layer  32  may be a fabric spacer or some other material layer that spaces the decorative layer  28  from the substrate  30 . 
       FIGS. 3 and 4  are CAE mold flow analyses that show the post-form warpage  42  that can occur during manufacture and be present after the foam layer  32  is introduced between the substrate  30  and the decorative layer  28 . Manufacturing the substrate  30  can cause undesirable post-form warpage if the substrate thickness (at least along the edge) is between 0.5 and 2.25 mm.  FIG. 3  shows the overall structure of a prior art substrate  30 ′ having a thin-walled structure of 2 mm. The CAE model shows the large deflection or warp, and along the windshield edge  18 ′, there is an area of post-form warpage  42 ′ that is about 18 mm (see scale on right side of  FIG. 3 ) in the Z direction. This amount of post-form warpage  42 ′, particularly at the windshield edge  18 ′ in the Z direction, can cause performance and/or installation problems. Advantageously, the amount of post-form warpage  42  should be less than 15 mm, or more particularly, less than 10 mm. This amount of post-form warpage  42  makes the interior panel  14  suitable for proper mating against the windshield  44  of the vehicle  12 . The XYZ axes are shown in the figures and correspond to the vehicle&#39;s longitudinal, lateral, and vertical axes once the panel  14  is installed in the vehicle  12 . 
     In the  FIG. 4  embodiment, the substrate  30  has a post-form warpage  42  along the windshield edge  18  that is about 8 mm (see scale on right side of  FIG. 4 ). Accordingly, the CAE modelling shows a 10 mm warp improvement in this particular embodiment. The post-form warpage  42  is the amount of warpage or deflection present at the edge region (or more particularly, at the windshield edge  18  or an alternate edge depending on the panel) before the panel  14  is installed in the vehicle  12 . Thus, the post-form warpage  42  can be measured by comparing the degree of warpage in the substrate  30  after it is fully manufactured (pre-install) with the nominal CAD data or the mold dimensions. The manufactured panels  14  can be scanned in a lab or gun-sighted, to cite a few examples, to ascertain the amount of post-form warpage  42  that is present. In another example, the panels  14 , before install, can be analyzed with a coordinate measuring machine (CMM) and the output is compared against the nominal CAD and/or a geometric dimensioning and tolerancing (GD&amp;T) system. In the illustrated embodiment, the post-form warpage  42  is the degree of warpage in the Z direction; however, with other vehicle panels, it may be desirable to control the degree of post-form warpage in other directions, depending on the way in which the panel is installed in the vehicle. 
     To achieve a suitable, minimal level of post-form warpage  42  on a thin-walled substrate having a thickness between 0.5 and 2.25 mm, or more particularly 2 mm in the illustrated embodiment, an edge region  46  near the windshield edge  18  is structurally modified to help impart rigidity to counteract the forces applied to the substrate  30  during manufacture. The edge region  46  includes the windshield edge  18  or another panel edge, an extension flange  48 , and a serpentine rib  50 . As detailed further below, the serpentine rib  50  can be integrally molded with a main body  52  of the substrate  30 . The substrate  30  is then put in a mold with the decorative layer  28 , and the panel  14 ,  16  is foamed to create the foam layer  32 . The serpentine rib  50  is then removed before the panel  14 ,  16  is installed in the vehicle  12 . In embodiments that include the serpentine rib  50  on an extension flange  48 , the extension flange  48  may also be removed before the panel  14 ,  16  is installed in the vehicle  12 . Removal can be accomplished via punching or milling, to cite a few examples. 
       FIGS. 5-7  more particularly illustrate the substrate  30  and the structural features of the edge region  46  such as the extension flange  48  and the serpentine rib  50 . The extension flange  48  starts at the windshield edge  18  and continues to a distal edge  54  where the serpentine rib  50  is located. The extension flange  48  can help keep the substrate  30  in the line of draw of the injection mold. The extension flange  48  has a primary arc  56  which corresponds in shape to the primary arc  58  of the windshield edge  18 , which matches the contour of the windshield  44  in the vehicle  12 . The serpentine rib  50  also has a primary arc  60  which matches the contour of the primary arc  56 , the primary arc  58 , and the contour of the windshield  44 . Each primary arc  56 ,  58 ,  60  is a single central curve that is configured to mimic the contour of the windshield  44 . 
     The extension flange  48  defines most of the area of the edge region  46  and extends from the windshield edge  18  toward the distal edge  54 . The extension flange  48  may have a different thickness than the thickness T of the substrate main body  52 , or it may have the same thickness. The extension flange  48  provides a small, generally planar area along the windshield edge  18  that can be milled, punched, or otherwise removed after the panel  14 ,  16  is foamed. In some embodiments, the extension flange  48  is located at an angle with respect to the body  52  at the windshield edge  18 . This, or scribe lines for example, can help demarcate the area to be removed after foaming and help create a cut line or indicator at the windshield edge  18 . 
     The serpentine rib  50  is located along a majority, or in this embodiment, an entirety of the distal edge  54  of the extension flange  48 . This arrangement provides increased structural rigidity at the edge region  46 , which can decrease the post-form warpage  42  in the Z direction at the windshield edge  18  so it is at a suitable amount (e.g., less than 15 mm or less than 10 mm, preferably). The serpentine rib  50  has a corrugated, sinusoidal shape with a plurality of undulations  62  (only a few are labeled for clarity purposes, and in the enlarged view of  FIG. 7 , each undulation is labeled as  62   a - f ). In this embodiment, there are no spaces between the undulations  62 , as each undulation goes straight into another undulation without breaks or straight gap portions between neighboring undulations. To be considered a “serpentine” rib, the rib needs to have three or more undulations that are uninterrupted by a straight or gap portion. Thus, with respect to the prior art embodiment shown in  FIG. 3 , this would not be a serpentine rib because there are straight gap portions between each undulation located on the windshield edge  18 ′. 
     The serpentine rib  50  projects up from the extension flange  48  in the Z direction, but it is possible to locate the serpentine rib  50  in different locations beyond that shown explicitly in the figures. For example, the serpentine rib could project down from the extension flange  48 , also in the Z direction. Or, the serpentine rib  50  may not be located on the extension flange  48 . In some embodiments the serpentine rib  50  could be located on the outer side  38  and/or inner side  40  along the main body portion  52  of the substrate  30 . If, for example, the serpentine rib  50  is located on the outer side  38 , it could then be milled or otherwise removed down to the outer side after foaming. The serpentine rib  50  may be completely orthogonal with respect to the extension flange  48 , or it may be angled (up to 25 degrees either way along the X axis from what is illustrated in the figures may still be considered to be extending in the Z direction). Projecting in the Z direction can make it easier to remove in a subsequent milling or punching operation. 
     The number of undulations  62  in the serpentine rib  50  will vary depending on the size and shape of the part being formed. In the illustrated embodiment, with a larger panel  14  such as the instrument panel  16 , more undulations are needed to help maintain the structural integrity of the larger edge  18 . Accordingly, more than 40 undulations are preferred with a panel comparable in size to an instrument panel. Other smaller panels will likely have less undulations. In some embodiments, however, smaller panels can have a comparable number of undulations to what is illustrated, just with a smaller pitch or wavelength λ. 
     With particular reference to  FIG. 7 , the serpentine rib  50  begins at the distal edge  54  and extends up to a top terminal edge  64  with the sinusoidal wall  65  extending therebetween. Each undulation  62  includes a peak  66  and a trough  68  with a sloped wall  70  located between the peak and the trough (only one undulation  62   b  is labeled with subcomponents for clarity purposes, but the teachings relating to the undulation  62   b  are also applicable to the other undulations as well). As discussed above, the plurality of undulations  62  are continuous, meaning that there is no straight gap or the like between adjoining undulations such that the sinusoidal wall  65  goes from peak  66  to sloped wall  70  to trough  68  to sloped wall to peak, etc. The peak angle α is between about 30° and 60° inclusive, or more particularly 45°, Having a peak angle α of 45°, as well as a trough angle of 45° as illustrated, can provide a more symmetrical structure that can be easier to manufacture. 
     In an advantageous embodiment, the ratio of the amplitude A to the pitch or wavelength λ is between 1:6 and 1:2, or more particularly in the illustrated embodiment, 1:4. In this embodiment in particular, the amplitude A is about 7 mm, and the wavelength is about 28 mm. This arrangement, again, can be easier to manufacture, particularly when integrally forming the serpentine rib  50  with the substrate  30  in an injection molding process. One potential reason for this is that the modifications needed in the tooling can be less cumbersome when creating this particularly sized serpentine rib  50 . These configurations for the undulations  62  were designed to strategically control the post-form warpage  42 , and verified using CAE mold flow analysis and injection trials. 
     It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims. 
     As used in this specification and claims, the terms “e.g.,” “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. In addition, the term “and/or” is to be construed as an inclusive OR. Therefore, for example, the phrase “A, B, and/or C” is to be interpreted as covering all the following: “A”; “B”; “C”; “A and B”; “A and C”; “B and C”; and “A, B, and C.”