Instrument Panel Resin Shrinkage Management
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Solution Overview
Problem
Conventional resin molding techniques for air bag doors integrated with instrument panels result in undesirable deformation due to differences in thermal shrinkage factors between the materials used, leading to a deterioration in the external appearance of the air bag door.
Innovation Solution
A resin component is designed with a first resin portion and a second resin portion having different thermal shrinkage rates, connected in a non-overlapping manner with a discontinuous portion at their boundary, allowing the deformation to be absorbed by the discontinuous area, which can be arranged intermittently along the boundary or on a surface opposite the designed surface, and includes features like V-shaped through holes to effectively manage shrinkage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different resin materials are used for the instrument panel and air bag door to match their respective technical properties, then the functional requirements of each component are satisfied, but deformation such as strain is generated in the air bag door due to difference in thermal shrinkage factor during cooling
Solution Approach 1:
The invention divides the resin component into multiple resin portions (first resin portion and second resin portion) with different thermal shrinkage characteristics. Each portion can shrink independently to different extents, allowing the overall component to accommodate differential shrinkage without generating harmful deformations. The discontinuous portion further segments the structure to enable independent deformation zones.
Solution Approach 2:
The invention changes the thermal shrinkage parameter by selecting different resin materials for different portions of the component. The first resin material and second resin material have different thermal shrinkage factors, allowing each portion to respond differently to temperature changes during cooling, thereby preventing uniform stress distribution that causes deformation.
2Productivity
If the air bag door is formed integrally with the instrument panel through injection molding to improve attaching work efficiency, then productivity is improved, but deformation such as strain is generated due to difference in thermal shrinkage factor between different resin materials
Solution Approach 1:
The integrated resin component is segmented into multiple portions with different thermal shrinkage characteristics. This segmentation allows each portion to accommodate its own shrinkage independently while maintaining integral formation through injection molding, thus preserving both productivity and dimensional accuracy.
Solution Approach 2:
The invention introduces dynamic deformation capability into the rigid integral structure by creating discontinuous portions and non-overlapping connections. These features allow the structure to dynamically adjust and absorb shrinkage stresses during cooling, preventing permanent deformations while maintaining the benefits of integral molding.
3Strength
If the second resin portion is surrounded by the first resin portion to connect the components, then the structural integrity is maintained, but the deformation is restricted from shrinking freely which tends to increase the deformation
Solution Approach 1:
The connection between resin portions is segmented into discrete non-overlapping connection portions rather than continuous contact. This segmentation allows controlled deformation at the boundaries while maintaining overall structural integrity, preventing stress concentration that would occur with continuous surrounding structures.
Solution Approach 2:
The discontinuous portion acts as an intermediary element between the first and second resin portions. It mediates the interaction between the two materials with different thermal shrinkage, allowing controlled deformation and stress distribution that maintains both structural integrity and dimensional accuracy.
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
The solution effectively absorbs deformation caused by thermal shrinkage differences between the resin portions, improving the external appearance of the resin component by managing strain and maintaining the integrity of the air bag door's design.
Implementation Method 1
different resin materials are selected for use. Consequently, in a conventional technique like one described in, for example, Patent Literature 1, when a product is molded by injecting resin materials and is then removed from a cavity for cooling, an undesirable deformation such as strain can be generated in an air bag door due to a difference in thermal shrinkage factor.
Data Source
AI summary
An instrument panel (10) includes a base material portion (20) made of a base material M1 and a different material portion (30) made of a different material M2 having a different thermal shrinkage from that of the base material M1, and in the instrument panel (10), the base material portion (20) and the different material portion (30) are connected in a state such that at least a part of the two materials do not overlap.