Monolithic Gas Generant Grain Density Optimization
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Solution Overview
Problem
Existing inflatable restraint systems, such as airbag inflators, face challenges in achieving optimal performance due to rapid pressure increase and excessive gas generant pressure, which can result in inadequate protection for out-of-position occupants, while also being costly and producing undesirable byproducts in effluent gases.
Innovation Solution
A method for forming a monolithic gas generant with high density and burn rate, free of polymeric binders, by admixing a gas generant material with a ballistic performance modifier and applying high pressures to achieve a pressed grain with a density greater than 95% of the theoretical maximum, optimizing combustion profiles and reducing effluent contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rate of pressure increase in the airbag is increased to improve response time, then the airbag deploys faster, but out-of-position occupants may not receive desired protection due to excessive pressure
Solution Approach 1:
The patent changes the physical and chemical parameters of the gas generant material by incorporating specific additives (e.g., metal powders, metal oxides, organic compounds) that modify the combustion characteristics. These parameter changes enable control over the rate of pressure increase, allowing the airbag to deploy rapidly while maintaining pressure within safe limits for out-of-position occupants.
Solution Approach 2:
The patent uses composite gas generant materials consisting of multiple components including fuel, oxidizer, and various additives in specific proportions. This composite structure allows for optimized combustion performance, achieving both rapid deployment and controlled pressure rise rates to protect out-of-position occupants.
2Reliability
If complex hardware systems are added to control gas flow and tailor gas generant performance, then gas generation control is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the control function from complex hardware systems and transfers it to the chemical composition of the gas generant itself. By incorporating performance-modifying additives directly into the propellant formulation, the system achieves reliable gas generation control without requiring additional hardware components, thereby reducing device complexity.
Solution Approach 2:
The gas generant material is designed to self-regulate its combustion characteristics through its chemical composition. The included additives enable the propellant to automatically control its own burning rate and gas generation profile, eliminating the need for external control systems and reducing overall device complexity.
3Strength
If polymeric binders are used in gas generant formulation to improve structural integrity, then handling safety is improved, but harmful byproduct compounds are produced in effluent gases
Solution Approach 1:
The patent changes the chemical composition parameters by replacing polymeric binders with alternative binding agents such as inorganic binders, natural polymers, or synthetic polymers with lower molecular weight. These substitutions maintain the necessary structural integrity for safe handling while significantly reducing or eliminating the production of harmful byproduct compounds during combustion.
Solution Approach 2:
The patent employs specific oxidizers and oxidation promoters in the gas generant formulation that ensure complete combustion of the binder materials. This accelerated oxidation minimizes the formation of incomplete combustion byproducts, allowing the use of polymer binders without producing harmful effluent compounds.
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 solution results in improved protection for occupants by achieving superior burn rates and gas yields with reduced production of harmful effluents, while simplifying the inflator system and reducing manufacturing costs, as the monolithic gas generant provides sustained combustion pressure without the need for multiple stages.
Implementation Method 1
The gas generants burn very rapidly to generate heated gas that inflates an airbag
Implementation Method 2
Pressure is applied to the gas generant material along both the first and the second sides to form a pressed monolithic grain
Data Source
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AI summary
Methods for making a pressed monolithic gas generant for an inflatable restraint device (for example, an airbag system for a vehicle) are provided. The methods include admixing a gas generant material with a ballistic performance modifier to form a mixture. The mixture is granulated. Then, a pressed monolithic gas generant grain is formed by applying pressure to the granulated mixture, where the grain has an actual density of at least about 95% of the maximum theoretical density. The pressure may be applied in a controlled manner to both side of the gas generant material in a die cavity, and removing formed grain from die cavity while maintaining some pressure to both sides of the grain, thereby further improving various pyrotechnic properties. The methods of the disclosure provide pyrotechnic compositions that are economical to manufacture, have improved burn rate, combustion profile, effluent quality, strength, durability, and integrity of the grain, while having a consistent shape between different production lots.