Automobile Cowl Grille Bending Deformation via Segmented Attachment
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Solution Overview
Problem
The existing cowl grille structure fails to effectively promote bending deformation when a load is applied from above, leading to inadequate pedestrian protection performance due to the rigid connection between the upper and front wall portions, which prevents separation and deformation.
Innovation Solution
The cowl grille is designed with a divided structure where the upper and front wall portions are separated by weak attachment piece portions, allowing for deformation by forming a cutout at the corner between the front wall body and attachment piece, reducing stiffness, and using glass fiber-containing polypropylene for the front wall portion to enhance thermal resistance while maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the upper wall portion and front wall portion are divided and fastened with screws, then the degree of freedom of designing in material selection is enhanced, but the bending deformation of the front wall portion is not promoted and pedestrian protection performance is insufficient
Solution Approach 1:
The cowl grille is divided into an upper wall portion and a front wall portion that are separable under load. The attachment piece portion is designed to rupture and separate from the front wall body portion when subjected to pedestrian impact, allowing the front wall portion to deform independently and absorb energy, thereby improving pedestrian protection while maintaining material selection flexibility.
2Strength
If the attachment piece portion is made rigid for strong fastening, then the fastening strength between upper and front wall portions is enhanced, but the stiffness reduction and separation capability under load is compromised
Solution Approach 1:
The attachment piece portion is designed with non-uniform thickness, creating a weak portion with reduced thickness at specific locations. This local quality variation allows the attachment piece to maintain adequate fastening strength in most areas while having specific weak points that rupture under pedestrian impact load, enabling separation and deformation of the front wall portion for energy absorption.
3Temperature
If the front wall portion is made of glass fiber-containing PP material for heat resistance, then the thermal resistance is enhanced, but the cost increases
Solution Approach 1:
The front wall portion is made of glass fiber-containing polypropylene material, while the upper wall portion uses standard polypropylene. This local material differentiation provides thermal resistance where needed (front wall near engine compartment) while controlling overall cost by using the more expensive material only in the necessary region.
Data Source
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AI summary
A resin cowl grille is provided to cover an upper portion of a cowl box. The cowl grille includes an upper wall portion and a front wall portion separated from the upper wall portion and provided with a bending promotion portion for inducing bending deformation upon action of load from above. The front wall portion includes a body portion and attachment piece portions extending backward from the body portion and fastened to a front portion of the upper wall portion. A weak portion for load in an upper-to-lower direction is formed by the attachment piece portion.