Open-Center Generant Holder for Lower-Pressure Airbag Inflators
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Solution Overview
Problem
Existing airbag inflator designs with tortuous paths for pressure waves require increased structural strength to manage higher internal operating pressures, leading to variability and safety concerns.
Innovation Solution
The design features a modified generant holder with an open center and annular ledge, allowing a clear path for pressure waves, combined with a generant cover and holes in the holder to control propellant burn and inert gas flow, optimizing ignition and reducing internal operating pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tortuous path structure is used for the pressure wave, then the pressure wave can be contained and directed, but the internal operating pressure increases and structural strength requirements increase
Solution Approach 1:
The patent removes the central obstruction from the generant holder, extracting the blocking structure that created the tortuous path. This allows the pressure wave to travel directly from the initiator through the center of the holder to the outlet burst disk, eliminating the need to withstand high internal operating pressures while maintaining pressure wave control
Solution Approach 2:
Instead of using a solid central structure to contain and redirect the pressure wave (traditional approach), the patent inverts the design by creating an open center configuration. The generant is positioned in an annular space around the open center, allowing the pressure wave to pass through the center unobstructed, thereby reducing structural strength requirements
2Reliability
If a tortuous path structure is used for the pressure wave, then the pressure wave can be contained, but the structural strength must be increased to offset higher internal operating pressures
Solution Approach 1:
The central obstruction is removed from the generant holder, extracting the structure that forced the pressure wave into a tortuous path. This eliminates the need for high structural strength to contain high internal operating pressures, while pressure wave containment is maintained through the annular generant configuration
Solution Approach 2:
The patent inverts the traditional solid-center design by creating an open center configuration. The generant is positioned annularly around the open center, allowing direct pressure wave transmission and reducing structural strength requirements while maintaining containment
3Speed
If the center of the generant holder is open, then the pressure wave can travel directly to the outlet burst disk, but the generant must be contained in an annular space
Solution Approach 1:
The generant holder is segmented into an annular space configuration, dividing the generant containment into a ring-shaped region around the open center. This segmentation allows direct pressure wave travel through the center while the annular generant provides controlled ignition around the periphery
Solution Approach 2:
The open center configuration serves multiple functions: it provides a direct path for the pressure wave to travel to the outlet burst disk, allows visual inspection of the initiator and pressure wave path, and enables the annular generant to burn uniformly from the outside in, ensuring complete combustion while simplifying the overall structure
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 approach results in a consistent burn of the generant, lower internal operating pressures, and enhanced safety factors, including reduced time to first gas and controlled pressure slope, addressing the limitations of previous designs.
Implementation Method 1
activating the initiator, which breaks through the initiator sleeve. This action serves to ignite the generant and allows the pressure wave to travel to the outlet burst disk to open the disk
Implementation Method 2
The inert gas flows out of the manifold into the airbag. The manifold chokes the flow of the gas controlling the slope and time to maximum pressure
Data Source
AI summary
An airbag inflator includes a pressure vessel, an initiator positioned at one end of the pressure vessel, a manifold positioned at an opposite end of the pressure vessel, and a generant holder assembly secured in the pressure vessel adjacent the initiator. The generant holder assembly defines an annular space that is configured to secure a generant. A center of the generant holder assembly is open. The open center allows a pressure wave from the initiator to travel to the outlet burst disk.