Dual-Chamber Gas Generator for Stable Airbag Pressure
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Solution Overview
Problem
Gas generators used in air bag systems face variations in output pressure due to environmental temperature, leading to inconsistent airbag deployment speeds, which can impact occupant protection.
Innovation Solution
A dual-type gas generator design with two combustion chambers and distinct gas discharge port groups, where the opening pressures and positions of the ports are strategically adjusted to maintain consistent output performance across varying temperatures, using a tubular housing with specific ratios of outer diameter to length and employing different seal members for each port group.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single combustion chamber is used, then the device complexity is low, but the output pressure varies significantly with environmental temperature
Solution Approach 1:
The combustion chamber is divided into two separate combustion chambers (first and second combustion chambers) with different gas generating agents. Each chamber has its own combustion characteristics that compensate for temperature variations, thereby stabilizing the overall output pressure while maintaining a relatively simple structure.
Solution Approach 2:
Different gas generating agents are used in different combustion chambers to optimize performance for specific temperature conditions. The first gas generating agent is used in the first combustion chamber and the second gas generating agent is used in the second combustion chamber, allowing each region to have tailored combustion properties that collectively stabilize output pressure across varying environmental temperatures.
2Reliability
If multiple gas discharge ports are used, then the output pressure control is improved, but the device complexity increases
Solution Approach 1:
The gas discharge ports are segmented into two distinct groups (first gas discharge port group and second gas discharge port group) with different opening pressures. This segmentation allows independent control of gas flow at different pressure stages, improving output pressure consistency while keeping the overall structure manageable through systematic design.
Solution Approach 2:
The opening pressures of the two gas discharge port groups are set to different values (P1 and P2), creating a staged pressure control mechanism. This parameter differentiation enables fine-tuned control of gas flow characteristics, maintaining consistent output pressure across varying environmental temperatures without requiring excessive structural complexity.
3Productivity
If the first gas discharge port group opens at high pressure, then the initial gas generation is rapid, but the overall output pressure becomes unstable
Solution Approach 1:
The gas discharge process occurs in two distinct stages through the two gas discharge port groups with different opening pressures. The first port group opens at pressure P1 and the second at pressure P2, creating a periodic, staged gas release pattern that maintains stable overall output pressure while ensuring rapid initial gas generation when needed.
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 ensures stable and reproducible output pressure, reducing the impact of environmental temperature on airbag deployment speed and maintaining uniform occupant protection performance.
Implementation Method 1
a burning rate (reaction rate) of a gas generating agent varies depending on the environmental temperature and, generally, the higher the temperature is, the faster the combustion becomes
Implementation Method 2
pressure (P1), that is necessary for opening the first gas discharge port group, and pressure (P2), that is necessary for opening the second gas discharge port group
Data Source
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AI summary
A gas generator (200) comprising: a tubular housing (212) having both ends (212a, 212b) closed and a gas discharge port (216a, 216b, 216c, 218) on a circumferential surface, and forming an outer shell of the gas generator (200), wherein a ratio (UD) of a diameter (D) and a length (L) of the tubular housing (212) of a portion that forms a first combustion chamber (270a) exceeds 1, a first closing member (230a) having an ignition device (25a) fixed thereto and closing one end of the tubular housing (212), a second closing member (230b) closing another end of the tubular housing (212), and a partition member (250) dividing a space between the first closing member (230a) and the second closing member (230b), among spaces (270a, 270b) divided by the partition member (250), a space (270a) that is closer to the first closing member (230a) and the ignition device (25a), serving as the first combustion chamber (270a) charged with a first gas generating agent (271a), a space (270b) that is closer to the second closing member (230b), serving as a second combustion chamber (270b) charged with a second gas generating agent (271b), the spaces (270a, 270b) satisfying a relationship where capacity of the first combustion chamber (270a) > capacity of the second combustion chamber (270b), the gas discharge port (216a, 216b, 216c), that is formed in a side of the first combustion chamber (270a), including at least two gas discharge port groups (216a, 216b, 216c), the at least two gas discharge port groups (216a, 216b, 216c) including a first gas discharge port group (216a) formed in the circumferential direction of the tubular housing (212) and closed, from the inside, by a seal member (217a), and a second gas discharge port group (216b) separated axially from the first gas discharge port group (216a), formed in the circumferential direction of the tubular housing (212) and closed, from the inside, by a seal member (217b), pressure (opening pressure P1), that is necessary for opening the first gas discharge port group (216a), and pressure (opening pressure P2), that is necessary for opening the second gas discharge port group (216b), satisfying a relationship of P1 < P2, the first gas discharge port group (216a) being positioned at a center portion in the axial direction between the first closing member (230a) and the partition member (250), or in the vicinity thereof, and the second gas discharge port group (216b) being positioned at a center portion in the axial direction between the first gas discharge port group (216a) and the partition member (250), or in the vicinity thereof.