Vehicle Cabin Covering Assembly With Seamless Material Junctions
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Solution Overview
Problem
Existing methods for producing vehicle interior coatings with multiple materials result in surface discontinuities and finishing defects at the junctions between materials due to viscosity changes and flow disturbances during injection, particularly near mold nozzles and with inserted elements.
Innovation Solution
A method involving the assembly of three sheets - an outer sheet with through openings, a flexible inner sheet, and a binder sheet - where the inner sheet is suctioned through the openings against a porous mold wall to ensure seamless junctions, using a thermoforming mold with suction mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If injection molding is used to insert first material into second material, then material combination is achieved, but surface discontinuities and finishing defects occur at junctions
Solution Approach 1:
The first material is pre-positioned against the inner face of the mold before injection, and the mold surface is pre-prepared with specific roughness characteristics. This preliminary arrangement ensures that when injection occurs, the materials will align properly at the junctions without creating surface discontinuities.
Solution Approach 2:
The invention changes the surface roughness parameter of the mold from smooth to specifically rough (Ra 0.4-2.5 μm), which fundamentally alters how the injected material flows and adheres to the mold surface. This parameter change enables the injected material to better match the peripheral contours of the first material, eliminating surface defects at junctions.
2Reliability
If injected material viscosity increases due to cooling, then material flow control is improved, but propensity to push second material against mold surface and fill spaces disappears
Solution Approach 1:
The invention modifies the thermal parameters of the system by changing the mold surface roughness, which affects heat transfer characteristics. The rougher surface reduces excessive cooling and viscosity increase near the injection nozzles, maintaining material flow propensities needed to push the second material against the mold surface and fill spaces effectively while still achieving surface continuity.
Solution Approach 2:
The mold surface is given different local qualities - specifically, different roughness characteristics in different zones. The areas near injection nozzles have roughness that prevents excessive cooling and viscosity buildup, while other areas maintain properties needed for proper material adhesion and surface matching. This local differentiation resolves the contradiction between flow control and surface matching.
3Ease of manufacture
If second material is pushed against mold surface to envelop first material, then material insertion is achieved, but surface discontinuities occur due to flow disturbances
Solution Approach 1:
By changing the mold surface roughness parameter to Ra 0.4-2.5 μm, the invention fundamentally alters the interaction between the injected second material and the mold surface. This roughness parameter enables the material to flow more uniformly and adhere better, eliminating surface discontinuities while maintaining the material insertion process. The rougher surface creates better mechanical interlocking and reduces flow disturbances that cause defects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method produces a covering assembly with continuous surface continuity at material junctions, eliminating defects and ensuring precise matching of peripheral contours without additional material addition, maintaining aesthetic integrity.
Implementation Method 1
a step of suctioning the inner sheet of the covering assembly at least on a portion of the outer face of the covering assembly which is not covered by the outer sheet, so that, through at least one through opening of the outer sheet, the outer surface of the inner sheet is positioned against the wall of the mold, at least level with the outer surface of the outer sheet, the suction being carried out through the porous wall of the mold
Data Source
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AI summary
The invention relates to a method for constructing a covering assembly for a vehicle passenger compartment, comprising at least: - overlaying, on the porous wall (8a) of a mould (8): • an external sheet (4) which is positioned at the side of the external face of the assembly in order to construct a first portion of the external face of the assembly, this external sheet (4) comprising through-openings (7) with the thickness of the sheet (4), • an internal sheet (5) which is positioned at the side of the internal face of the covering assembly, the internal sheet (5) having a flexibility greater than that of the material of the external sheet (4), • a sheet (6) which is made of binder material and which is arranged between the external sheet (4) and internal sheet (5), - drawing in the internal sheet (5) through at least one opening (7) of the external sheet (4).