Knee-Airbag Bracket Design for Load Dispersion
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Solution Overview
Problem
Existing knee-airbag device attachment structures face a trade-off between achieving high support rigidity for occupant protection during vehicle collisions and minimizing vehicle weight, as increasing rigidity often leads to increased weight and reduced fuel economy.
Innovation Solution
The knee-airbag device is connected and supported at both the instrument panel member and the instrument panel core, with a vehicle-body side bracket and branch bracket configuration that disperses the inflation load efficiently, allowing for high support rigidity while keeping the attachment structure lightweight by using a short, high-rigidity vehicle-body side bracket and an additional branch bracket.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the plate thickness of the support member is increased or a high-rigidity member is used to increase the rigidity of the attachment structure, then the support rigidity during airbag inflation is improved, but the vehicle weight increases and fuel economy deteriorates
Solution Approach 1:
The attachment structure is divided into multiple segments: the instrument panel member, the floor brace extending from it, and the knee-airbag device connecting both. This segmentation allows the load to be distributed across multiple structural components rather than concentrating it in a single thick support member, achieving high rigidity without excessive weight in any one component.
Solution Approach 2:
The support structure transitions from a two-dimensional planar bracket to a three-dimensional spatial framework by adding the floor brace that extends vertically and diagonally from the instrument panel member to the tunnel portion. This spatial configuration creates a triangulated support system that provides high rigidity through geometric stability rather than relying on increased plate thickness.
2Strength
If a short, high-rigidity vehicle-body side bracket is used to achieve high support rigidity, then the rigidity during inflation is improved, but the weight may increase
Solution Approach 1:
The vehicle-body side bracket is designed with optimized parameters including its length, plate thickness, and attachment positions. By carefully selecting these parameters, the bracket achieves the minimum necessary rigidity for safe operation while minimizing weight. The bracket connects the knee-airbag device to the vehicle body at strategically chosen locations to maximize structural efficiency.
3Device complexity
If the knee-airbag device is connected only to the instrument panel member, then the device complexity is reduced, but the support rigidity during inflation is insufficient
Solution Approach 1:
The attachment structure is divided into multiple segments: the instrument panel member, the floor brace extending from it, and the knee-airbag device connecting both. This segmentation allows the load to be distributed across multiple structural components rather than concentrating it in a single thick support member, achieving high rigidity without excessive weight in any one component.
Solution Approach 2:
The support structure transitions from a two-dimensional planar bracket to a three-dimensional spatial framework by adding the floor brace that extends vertically and diagonally from the instrument panel member to the tunnel portion. This spatial configuration creates a triangulated support system that provides high rigidity through geometric stability rather than relying on increased plate thickness.
Data Source
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AI summary
In a knee-airbag-device attachment structure of a knee-airbag device 20, an instrument-panel-member side bracket 22 which connects the knee-airbag device 20 and an instrument panel member 2 to support the knee-airbag device 20 comprises a branch bracket 22B which is connected to an instrument panel core 4. The knee-airbag-device attachment structure further comprises a vehicle-body side bracket 21 which connects the knee-airbag device 20 and a hinge pillar 1B of a vehicle body 1.