Filterless Gas Generator Ignition and Filtration Design
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Solution Overview
Problem
Existing gas generators for vehicle restraining devices face challenges in improving the ignition properties of gas generating agents, particularly due to uneven ignition patterns and the difficulty in forming inclined holes, which affects the ejection-direction regulating function and increases weight.
Innovation Solution
A gas generator design featuring a cup-shaped housing with a cup-shaped inner tube member and an igniter attaching portion, where the combustion product passage is formed between the inner tube member and the igniter attaching portion, allowing ignition to start from the bottom surface, enhancing ignition properties and eliminating the need for filters or coolants by using a porous member to filter and cool combustion residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inclined hole is formed on the circumferential wall surface of a cylindrical member to discharge combustion products, then the ejection-direction regulating function is improved, but it is difficult and troublesome to form the inclined hole and increases manufacturing complexity
Solution Approach 1:
Instead of forming an inclined hole in the conventional cylindrical member, the patent inverts the approach by forming the hole at the bottom of the igniter and creating a vertical passage through the inner cylindrical body. This simplifies manufacturing while maintaining effective combustion product ejection direction control.
Solution Approach 2:
The patent extracts the hole-forming operation from the circumferential wall surface of the cylindrical member and relocates it to the bottom of the igniter. This separation allows for easier formation of the hole and passage using standard drilling operations rather than complex inclined hole formation.
2Strength
If a thicker cylindrical member is used to maintain ejection-direction regulating function, then the structural integrity is improved, but the weight of the gas generator increases
Solution Approach 1:
The patent inverts the conventional design by placing the hole at the bottom of the igniter rather than in the cylindrical member wall. This allows for a thinner cylindrical member that maintains structural integrity while enabling effective combustion product ejection through the igniter and inner cylindrical body passage.
Solution Approach 2:
The patent utilizes the inner cylindrical body as a porous-like structure with a passage through it, allowing combustion products to pass through while maintaining a thin wall design. This eliminates the need for a thicker cylindrical member and reduces overall weight.
3Strength
If conventional welding is used to assemble the gas generator components, then the structural strength is improved, but the assembly process becomes more complex and time-consuming
Solution Approach 1:
The patent merges the igniter attaching portion with the closure shell by forming it as an integral cylindrical portion projecting from the closure shell. This eliminates the need for separate welding operations to attach the inner cylindrical body, simplifying assembly while maintaining structural strength through the integrated design.
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 improves the ignition properties of the entire gas generating agent, reduces the size and weight of the gas generator, and simplifies assembly by eliminating the need for conventional welding, while effectively filtering and cooling combustion residues.
Implementation Method 1
when the igniter is activated, a flame and the like are ejected from a hole formed in the cylinder to the combustion chamber, whereby the gas generating agent is ignited
Implementation Method 2
the combustion chamber having an outer circumferential surface formed by an outer circumference cylindrical member, an inner circumferential surface formed by the inner tube member, a bottom surface formed by the bottom plate of the closure shell and a top surface formed by a an annular porous member
Implementation Method 3
a gas discharge path formed between the outer circumference cylindrical member and a side surface of the diffuser shell; and the space and the gas discharge path being communicated with each other
Data Source
Figure 1~2
Figure 3~5(b)
Figure 6~7
AI summary
The present invention provides a filterless gas generator (10), including a housing having a closure shell (13), a diffuser (12) and a flange portion (12b), an inner tube member (20) accommodating an igniter (31) coaxially with the central axis of the housing, an opening end (29) of the inner tube member located in a bottom plate (13a) of the closure shell and a ventilating portion (27) formed at the opening end (29), the inner tube member fixed to an igniter attaching portion (13c), being a cylindrical portion projecting inwardly in the closure shell, and a passage being formed between the inner tube member and the igniter attaching portion to reach the ventilating portion, an annular porous member (50) disposed and defining a space (60) above the combustion chamber, the space communicating to a gas discharge path (16) between an outer circumference cylindrical member (42) and a side surface of the diffuser shell through a communicating portion (45).