Automobile Hood Inner Panel Airspace for Pedestrian Protection
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Solution Overview
Problem
Existing automobile hoods face challenges in achieving both sporty design and pedestrian protection performance due to limited space under the hood, where the secondary impact acceleration is higher and longer, negatively affecting the Head Injury Criterion (HIC) value, making it difficult to meet both basic performance requirements and pedestrian protection standards.
Innovation Solution
The automobile hood features a cross-sectional structure with interposed airspace portions between the outer and inner panels, incorporating a frame-shaped first inner member with a concave section and a second inner member with extension portions that form airspace portions, enhancing energy absorption during primary impacts and reducing secondary impact acceleration while maintaining tensile rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the space under the hood is reduced to achieve sporty design and accommodate larger engines, then the engine output and functional parts are improved, but the pedestrian protection performance deteriorates due to insufficient energy absorption space
Solution Approach 1:
The inner panel is divided into multiple regions with different concave portion configurations. The peripheral part has a first concave portion for energy absorption, while the center part has a second concave portion with different characteristics. This segmentation allows each region to optimize for its specific function while working together for overall pedestrian protection.
Solution Approach 2:
Different regions of the inner panel are given different local characteristics through varying concave portion depths and shapes. The peripheral region has deeper concave portions for initial impact energy absorption, while the center region has shallower portions to control secondary impact. This local differentiation enables optimized energy management throughout the impact process.
2Use of energy by moving object
If deeper concave portions are formed on the inner panel to increase energy absorption, then the primary impact energy absorption is improved, but the secondary impact acceleration increases and the HIC value deteriorates
Solution Approach 1:
The energy absorption process is segmented into two phases through spatial segmentation of the concave portions. The first concave portions handle primary impact energy absorption, while the second concave portions are positioned and sized to control the secondary impact phase, preventing excessive acceleration.
Solution Approach 2:
The concave portions are pre-configured with specific depths and positions to provide cushioning effects before impact occurs. The peripheral concave portions are designed to deform in a controlled manner during primary impact, absorbing energy before it can transmit to the pedestrian's head, thereby reducing secondary impact acceleration.
3Use of energy by moving object
If the concave portion depth is increased to improve energy absorption, then the energy absorption capacity is improved, but the tensile rigidity and bending stiffness of the hood deteriorate
Solution Approach 1:
The inner panel's concave portions are segmented into different depth zones and spatial locations. By distributing the deformation capacity across multiple shallower concave portions rather than one deep concave portion, the overall structural rigidity is maintained while achieving sufficient energy absorption capacity.
Solution Approach 2:
The concave portions are strategically positioned and sized with different local depths based on their function. Peripheral concave portions have greater depth for energy absorption, while maintaining overall panel rigidity through the distributed configuration and connection to the reinforcement members.
4Strength
If reinforcement members are added to the inner panel to improve tensile rigidity, then the basic performance requirements are improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The reinforcement members are merged with the inner panel structure itself, forming an integrated component rather than separate attachments. The reinforcement ribs are formed as integral parts of the inner panel during molding, combining the functions of the inner panel and reinforcement members into a single piece, thereby reducing assembly steps and manufacturing complexity.
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 design effectively reduces secondary impact acceleration, improves pedestrian protection performance by lowering the HIC value, and ensures the hood meets basic performance requirements such as tensile rigidity and bending stiffness, while also being lightweight and cost-effective.
Implementation Method 1
The automobile hood has a cross-sectional structure in which airspace portions are interposed at predetermined positions between the outer panel and the inner panel when the both panels are joined, wherein the inner panel includes a frame-shaped first inner member joined with the peripheral part of the outer panel and having a concave sectional shape
Data Source
AI summary
An automobile hood includes an outer panel and an inner panel. The inner panel includes a frame-shaped first inner member that joins with the outer panel and a second inner member disposed within the frame of the first inner member. The first inner member includes an outer edge portion, a first inner concave portion that forms an airspace portion, and an inner edge portion. The second inner member includes a second inner concave portion that has joint portions that join with the first inner member and form the airspace portions, panel joint portions that join with the outer panel at position on a center side of the panel, and an extension portion that extends into the first inner concave portion to join with the outer panel.