Jacketed Fuel Tablet Structure for Controlled Ignition and Burn Rate
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Solution Overview
Problem
Existing fuel elements for gas generators in safety devices face challenges in achieving optimal combustion characteristics, leading to inconsistent deployment of gas bags during vehicle accidents, due to limitations in controlling burn-off properties such as burn rate and ignitability.
Innovation Solution
A coated tablet fuel element design featuring a core made of a first pyrotechnic material surrounded by a jacket layer of a second pyrotechnic material, with a geometric edge section that extends radially and axially, allowing controlled exposure and ignition, thereby regulating combustion characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coated tablet with a completely enclosing coating layer is used, then the combustion characteristics can be controlled, but the core material cannot be sufficiently exposed for consistent ignition
Solution Approach 1:
The coating layer is segmented to create an edge portion that is open or partially open, allowing the core material to be exposed at the edge while maintaining coverage in other areas. This segmentation enables both controlled combustion and reliable ignition by providing a designated exposure zone.
Solution Approach 2:
Different regions of the coated tablet have different properties: the majority of the coating layer provides combustion control, while the edge portion provides ignition access. This local differentiation allows the tablet to achieve both consistent burn-off characteristics and reliable ignitability.
2Ease of manufacture
If the core material is fully exposed to enable ignition, then ignitability improves, but degressive burning occurs leading to inconsistent combustion
Solution Approach 1:
Instead of fully exposing the core material, only a portion of it is exposed at the edge portion. This partial exposure provides sufficient access for ignition while maintaining the coating layer's ability to control combustion and prevent degressive burning in the bulk material.
Solution Approach 2:
The coating layer transitions from fully enclosing the core to being open at the edge portion, creating localized differences in material exposure. This allows the edge area to support ignition while the covered areas maintain combustion consistency.
3Reliability
If a multi-layer tablet structure is used to control burn rate, then combustion characteristics improve, but the device complexity increases
Solution Approach 1:
The tablet is divided into a core material and a coating layer, with the coating layer itself segmented to create an open edge portion. This segmentation provides combustion control without requiring multiple separate layers, simplifying the overall structure compared to traditional multi-layer designs.
Solution Approach 2:
The tablet uses a composite structure of core material and coating layer materials with different combustion properties. This composite approach enables control of burn rate and combustion characteristics while maintaining a relatively simple two-component structure rather than multiple layers.
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
The design ensures improved control over combustion characteristics, preventing degressive burning and enhancing ignitability, resulting in more consistent and effective gas deployment for safety devices.
Implementation Method 1
When activated by an electrical igniter, they undergo an exothermic reaction, releasing the compressed gas into the gas bag
Implementation Method 2
they undergo an exothermic reaction, releasing the compressed gas into the gas bag
Data Source
Figure 1~4
Figure 5~7
Figure 8~10
AI summary
The invention relates to a propellant element for a gas generator for use in a safety device in the form of a jacketed tablet (24), wherein the jacketed tablet (24) comprises a core (20) made of a first pyrotechnic material (46) and a jacket layer (22) enclosing the core (20) made of a second pyrotechnic material (48), wherein the first pyrotechnic material (46) differs from the second pyrotechnic material (48) and wherein the core (20) has a radially projecting edge section (26) which extends through the jacket layer (22) to an outer contour (28) of the jacketed tablet (24), wherein the edge section (26) is formed along a circumferential direction of the jacketed tablet (24) and has a smaller extent in the axial direction of the jacketed tablet (24) than the core (20).