Airbag Module Fragment Restraint via Ignition Cable
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Solution Overview
Problem
Conventional gas bag modules with pyrotechnic actuator units face challenges in increasing functional reliability due to oversized and expensive metal explosive bolts, which are not suitable for the low shearing force loads required, and uncontrolled movement of severed fragments during deployment, potentially causing damage.
Innovation Solution
The use of a restraining means, such as an ignition cable or cable tie, to limit the movement of the severed fragment, which is integrated into the actuator unit's design to prevent free movement and secure the fragment outside the gas bag chamber, utilizing existing components like the ignition cable for power supply and restraint, and providing securing elements to enhance mechanical load capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional metal explosive bolts are used to attach the actuator unit, then the connection strength is sufficient, but the device becomes oversized and too expensive for the application
Solution Approach 1:
The actuator unit housing is divided into two parts: a fastening section that remains attached to the module and a detachable section that forms the separated fragment. This segmentation allows using a lighter, less expensive fastening section while the detachable section is designed to break away controllably, resolving the contradiction between connection strength and device complexity/cost.
Solution Approach 2:
The fastening section incorporates a predetermined breaking point with specific mechanical properties that allow it to withstand assembly and operational loads but fail at a controlled location during deployment. By changing the structural parameters at this breaking point, the system achieves sufficient connection strength during installation while enabling fragment separation to reduce overall device complexity and cost.
2Ease of operation
If the actuator unit is designed to break into separated fragments upon triggering, then the deployment function is achieved, but the severed fragment may move freely and cause damage to the module
Solution Approach 1:
A restraining means (such as a cable or tether) acts as an intermediary between the detachable section and the module housing. This intermediary allows the actuator unit to deploy by separating the fragment while simultaneously preventing the fragment from moving freely and causing damage, thus resolving the contradiction between deployment functionality and harm prevention.
Solution Approach 2:
The restraining means is pre-installed on the detachable section before deployment. This preliminary anti-action counteracts the potential harmful movement of the fragment before it can cause damage, allowing the fragment to separate for proper deployment while being simultaneously constrained to prevent harmful effects.
3Object-affected harmful factors
If additional restraining components are added to control fragment movement, then the harmful effects are reduced, but the device complexity increases
Solution Approach 1:
The ignition cable serves multiple functions: it provides electrical connection for triggering the actuator unit and simultaneously acts as the restraining means to limit fragment movement. By making the ignition cable multi-functional, the system reduces the number of separate components needed, thus preventing fragment damage without significantly increasing device complexity.
Solution Approach 2:
The restraining function is merged with the existing ignition cable rather than being implemented as a separate component. This combining of functions eliminates the need for additional restraining components, achieving harm prevention while maintaining simplicity in the overall device 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
This solution enhances the functional reliability of the gas bag module by restricting the movement of severed fragments, preventing damage and reducing the risk of unintentional loosening, while eliminating the need for additional components and ensuring the fragment remains outside the gas bag chamber during deployment.
Implementation Method 1
a pyrotechnic actuator unit (16), which is attached to a module component (12, 44) by a fastening section (22)
Data Source
Figure 1a~1b
Figure 2~3
Figure 4~5
AI summary
The invention relates to an airbag module (10) for a vehicle safety system, comprising an airbag (48), a gas generator (12), a module housing (46) and a pyrotechnic actuator unit (16), which is attached to a module component by means of a fixing portion (22), the area that is supplied with an internal pressure during the activation of the gas generator and that is at least partly delimited by the interior of the airbag is defined as an airbag chamber (52). The actuator unit (16), once triggered is broken up into the fixing portion (22) that is fixed to the module component and at least one separated fragment (24), the latter (24) being located outside the airbag chamber (52). The module is provided with a restraining element (30) that limits the freedom of movement of the separated fragment (24).