Gas Generator Igniter Collar Hardness Ratio
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Solution Overview
Problem
Existing gas generators for airbag systems face challenges in maintaining sufficient contact strength between cup members and collars, especially under low-temperature conditions, leading to reduced pressure resistance and adhesion issues during press-fitting.
Innovation Solution
The gas generator employs a specific ratio of Vickers hardness between the igniter collar and the ignition/combustion chamber cup, within the range of 0.25 to 0.65, achieved through annealing and material selection, to enhance the press-fitting process and adhesion between the cup members and igniter collars, facilitating efficient assembly and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength steel sheet is used for housing and press-molding is performed, then strength is improved, but pressure resistance cannot be maintained under low-temperature environment
Solution Approach 1:
The invention changes the material parameter by using ordinary steel sheet instead of high-strength steel sheet, and controls the Vickers hardness of the cup member within a specific range (100-200 HV) to achieve both strength and pressure resistance under low-temperature conditions without requiring annealing treatment
2Strength
If annealing treatment is performed on high-strength steel housing, then low-temperature strength is improved, but pressure resistance is lost
Solution Approach 1:
The invention avoids annealing treatment by using ordinary steel sheet and controlling the cup member's Vickers hardness to 100-200 HV, thereby maintaining pressure resistance while achieving sufficient low-temperature strength through the hardness-controlled cup member design
3Ease of manufacture
If press-fitting is performed without specific hardness control, then assembly is simplified, but contact strength between cup member and collar is insufficient
Solution Approach 1:
The invention maintains assembly simplicity by using press-fitting while improving contact strength through specific hardness control of the cup member (100-200 HV), creating an optimal hardness differential with the collar that ensures sufficient bonding strength during press-fitting
4Ease of manufacture
If Vickers hardness ratio of cup member to collar is outside 0.25-0.65 range, then material selection is easier, but adhesion during press-fitting deteriorates
Solution Approach 1:
The invention specifies that the Vickers hardness of the cup member should be 100-200 HV to achieve an optimal hardness ratio (0.25-0.65) relative to the collar, ensuring sufficient adhesion strength during press-fitting while maintaining reasonable material selection flexibility
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 ensures tight adhesion and efficient operability during press-fitting, maintaining pressure resistance and improving the overall performance of the gas generator, even under low-temperature conditions.
Implementation Method 1
an inner circumferential wall surface on an opening side of an ignition device chamber cup, which is charged with the transfer charge, is press-fitted to and in close contact with an outer circumferential wall surface of the igniter collar of the igniter
Implementation Method 2
where such annealing treatment is performed, a pressure resistance, that is, needed to withstand the increase in internal pressure inside the working gas generation chamber, cannot be maintained
Data Source
AI summary
A gas generator includes, inside a housing, an ignition device chamber accommodating a transfer charge and an igniter in which an igniter main body is surrounded by an igniter collar. The ignition device chamber is formed such that an inner circumferential wall surface on an opening side of an ignition device chamber cup, which is charged with the transfer charge, is press-fitted to and in close contact with an outer circumferential wall surface of the igniter collar of the igniter. The ratio (Vh2/Vh1) of an average Vickers hardness (Vh1) of the igniter collar, which is measured by a method described in Examples, and an average Vickers hardness (Vh2) of the ignition device chamber cup, which is measured by a method described in Examples, is within a range of 0.25 to 0.65.