Breakaway Engine Cradle Fasteners for Deceleration Control
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Solution Overview
Problem
Current vehicle front shock absorption systems face challenges in satisfying both frontal impact tests at 40% overlap on a deformable obstacle and 100% overlap on a rigid obstacle, leading to increased risk of intrusions and degraded occupant biomechanical protection due to excessive deceleration, which existing technologies struggle to manage efficiently and economically.
Innovation Solution
A motor vehicle structure featuring a floor with an engine cradle fixed via breakaway fastening means that break during frontal impacts, allowing the cradle to move rearward, specifically designed to prevent breakage during impacts at 30-50% overlap on a deformable obstacle and ensure breakage during 100% overlap on a rigid obstacle at 50 km/h, utilizing screw-nut type fasteners with zones of weakening to control deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the engine cradle is fixed rigidly to the floor via conventional fixing means, then the structural strength and stability are improved, but the deceleration forces during frontal impact increase excessively, degrading occupant biomechanical protection
Solution Approach 1:
The fixing means parameters are changed by introducing zones of weakening (reduced cross-section) at specific locations. This allows the fastening means to maintain full strength during normal operation but break at controlled locations during impact, transforming the rigid connection into a programmatically breakable one that limits deceleration forces.
Solution Approach 2:
The fastening means are segmented into distinct zones: strong zones for normal load bearing and weakened zones for controlled breakage. This segmentation allows the system to provide both structural strength during normal use and deceleration control during impact by breaking at predetermined locations.
2Object-affected harmful factors
If breakaway fixing means are used to limit deceleration forces, then occupant protection is improved, but the structural stability and intrusion prevention are worsened due to increased risk of cradle movement
Solution Approach 1:
The zones of weakening are pre-positioned at optimal locations in the fastening means before impact occurs. This preliminary arrangement ensures that when impact happens, the breakage occurs at predetermined locations that have been designed to limit cradle movement while controlling deceleration, thus maintaining both occupant protection and structural stability.
Solution Approach 2:
The zones of weakening act as intermediaries that control the energy transfer during impact. By breaking at these controlled locations, they mediate between the rigid structure and the cradle, allowing controlled movement that limits deceleration forces while preventing uncontrolled intrusion into the passenger compartment.
3Object-affected harmful factors
If pyrotechnic charges are used to trigger programmed breaking fasteners, then deceleration control is improved, but the device complexity and cost increase significantly
Solution Approach 1:
The fastening means are designed to break automatically during frontal impact without requiring external activation systems. The zones of weakening cause the fasteners to fail at predetermined loads, making the system self-activating and eliminating the need for pyrotechnic charges, sensors, or control systems while maintaining deceleration control.
Solution Approach 2:
The fastening means with zones of weakening are designed as simple, inexpensive components that break during impact. This disposable approach replaces expensive pyrotechnic systems with simple mechanical features that achieve the same deceleration control function at much lower cost and complexity.
4Ease of manufacture
If conventional fixed fastening means are used, then manufacturing simplicity is maintained, but the ability to satisfy both 40% overlap deformable obstacle test and 100% overlap rigid wall test is compromised
Solution Approach 1:
The fastening means have non-uniform cross-sections with localized zones of weakening at specific positions. This local quality change allows the same component to satisfy both test protocols: the weakened zones break during 100% overlap rigid wall impacts to limit deceleration, while the overall structure maintains integrity during 40% overlap deformable obstacle tests.
Data Source
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Figure 5~9
AI summary
The invention relates to a structure (2) of a motor vehicle, comprising: a floor (10); an engine cradle (18) with a rear part attached to the floor (10) via fastening means (22), the rear fastening means (22) being releasable fastening means designed to break in the event of a head-on impact, allowing said cradle (18) to move towards the rear along said floor (10). The invention also relates to a vehicle comprising such a structure (2).