Adaptive Vehicle Safety Belt Force Limiting via Segmented Piston Tube
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Solution Overview
Problem
Existing seat belt devices struggle to adapt the force characteristic of the belt force limiting unit to accommodate variations in occupant size, weight, and seating position, leading to inefficient force limitation during crashes.
Innovation Solution
A seat belt device equipped with a switching unit that adjusts the force limitation level via a pyrotechnically activated loop-shaped clamp around the piston tube, connected to a crash sensor and occupant detection system, allowing for real-time adaptation of the force profile based on occupant characteristics before a crash occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the piston tube has varying internal cross section with axial webs made of same material formed in one piece, then the force characteristic can be set, but the production cost increases and factory modification requires great tooling
Solution Approach 1:
The piston tube is divided into multiple axially arranged tube segments with different wall thicknesses. Each tube segment can be produced separately and then joined together, allowing easy adjustment of the force characteristic by changing the combination of segments. This segmentation enables factory modification without requiring complex tooling, as segments can be reconfigured by simple assembly changes rather than requiring the entire tube to be remanufactured.
Solution Approach 2:
The system transitions from a static, fixed force characteristic to a dynamic, adjustable one. By providing multiple tube segments with different wall thicknesses that can be selectively combined, the force characteristic can be adapted to different occupancy conditions. This dynamic adaptability is achieved through a simple segmentation approach that avoids the high production costs and tooling requirements of traditional varying cross-section designs.
2Adaptability or versatility
If the material thickness of the piston tube is increased in the axial direction, then the force limitation level can be adjusted, but the device complexity and production cost increase
Solution Approach 1:
Instead of creating a complex continuously varying wall thickness throughout the piston tube, the design segments the tube into discrete sections with different wall thicknesses. This segmentation simplifies the manufacturing process and reduces structural complexity while still achieving the desired force limitation adjustment. Each segment can be produced using standard manufacturing processes and then joined together.
Solution Approach 2:
Different sections of the piston tube are given different wall thicknesses according to the specific force characteristic requirements. Rather than uniformly increasing the wall thickness throughout the entire tube, the local quality principle allows each axial section to have the appropriate thickness for its specific function, optimizing performance while minimizing overall complexity and material usage.
3Ease of manufacture
If a fixed force characteristic is used in the piston tube, then the manufacturing is simple, but the force limitation cannot be adapted to different occupant sizes, weights and seating positions
Solution Approach 1:
The piston tube is constructed from multiple standardized tube segments that can be produced using simple, consistent manufacturing processes. The adaptability is achieved not by complex manufacturing variations but by the modular assembly of these segments in different combinations. This maintains manufacturing simplicity while enabling force characteristic adaptation through configuration changes rather than production complexity.
Solution Approach 2:
The same basic tube segment design serves multiple functions by being used in different combinations and positions. A single type of segmented construction can provide multiple force characteristics depending on how the segments are arranged and connected. This universal segmented approach allows one manufacturing process to produce components that can be configured for different occupancy conditions.
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 a tailored force limitation that prevents abrupt impacts on the piston stop, particularly for larger occupants, by dynamically adjusting the piston tube's component strength, thereby enhancing safety and comfort during accidents.
Implementation Method 1
The tightening unit (30) is designed, in particular in the form of a pyrotechnic tightening unit, by means of which the tensile force can be applied to the pull tab (48) of the clamp (28)
Implementation Method 2
the piston is displaced in the axial direction by a force limitation path, with expansion and plastic deformation of the piston tube, as a result of which the belt force exerted on the vehicle occupant is limited
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a safety belt device for a vehicle, having a belt force limiting unit (13), which is designed as a piston/cylinder arrangement comprising a piston tube (23) and a piston (25), which in the event of the belt force being limited, in particular in the event of a crash, can be displaced in the piston tube (23) for a force limiting distance (s) while expanding and being plastically deformed, such that the belt force (F) exerted on a vehicle occupant is limited to a pre-defined force level. According to the invention, the safety belt device has a switching unit (36), by means of which, in particular in a pre-crash phase, the force level profile (F(s)) can be predefined via the force limiting distance (s) depending on the height and/or the weight and/or the sitting position of the vehicle occupant.