Knee Airbag Overflow Opening for Pressure Control
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Solution Overview
Problem
Knee airbags require higher gas generator pressures to achieve rapid deployment and filling, leading to increased pressure peaks that can cause integrity issues with the airbag material, and existing designs do not effectively prevent backflow of deployment gas from the knee region.
Innovation Solution
A knee airbag with a closable overflow opening between chambers, where the overflow opening is mechanically closed by the penetrating knees, preventing backflow and maintaining pressure within the chamber for effective support, using catch straps or dividing wall bushings to block the overflow opening upon knee contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If higher gas generator pressure is used to achieve rapid deployment and filling of knee airbag chambers, then deployment speed and filling efficiency are improved, but pressure peaks increase causing material integrity problems
Solution Approach 1:
The knee airbag is divided into multiple chambers (first chamber, second chamber, third chamber) separated by dividing walls with controlled overflow openings. This segmentation allows deployment gas to be distributed sequentially through overflow openings at different heights, enabling rapid filling of multiple regions without requiring excessively high gas generator pressure, thus resolving the contradiction between deployment speed and material integrity.
Solution Approach 2:
The overflow openings are designed to close dynamically under pressure differential. When pressure in the first chamber exceeds a threshold, the overflow opening closes automatically, creating a pressure peak that accelerates filling of subsequent chambers. This dynamic closure mechanism enables rapid deployment while controlling the duration and magnitude of pressure peaks to protect material integrity.
2Productivity
If overflow opening remains open to allow gas flow between chambers, then filling efficiency is improved, but backflow of deployment gas from knee region occurs reducing support effectiveness
Solution Approach 1:
The overflow opening is designed as a dynamic closure mechanism that responds to pressure differential. During normal filling, the opening remains open allowing efficient gas flow from the first chamber to subsequent chambers. When knee penetration occurs and pressure in the second chamber rises, the pressure differential causes the overflow opening to close automatically, preventing backflow and maintaining support effectiveness in the knee region.
Solution Approach 2:
The system uses pressure differential as feedback to control the state of the overflow opening. When pressure in the second chamber approaches or exceeds pressure in the first chamber, the pressure differential triggers closure of the overflow opening, preventing harmful backflow. This feedback mechanism ensures the opening remains open during efficient filling but closes automatically when knee contact occurs, maintaining both filling efficiency and support reliability.
Data Source
AI summary
A knee airbag having an inlet opening (6) for deployment gas from a gas generator (4) for flowing into a first chamber (10), at least one second chamber (20, 30) adjacent to the first chamber (10), which second chamber (20, 30) is separated from the first chamber by at least one dividing wall (25), wherein between the first chamber (10) and the second chamber (20, 30) at least one closable overflow opening (40) is provided, through which deployment gas can flow from the first chamber (10) into the second chamber (20, 30), wherein at least one closing device (50 for the overflow opening (40), or the overflow opening (40), is associated with the penetration region of the knees (5).