Coaxial Belt Retractor Structure for Narrow Backrest Space
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Solution Overview
Problem
Belt retractors designed for installation in vehicle backrests face challenges due to limited space, requiring a compact and elongated structure to absorb tensile forces during accidents, while maintaining a rigid framework with minimal dead weight.
Innovation Solution
The belt reel, first torsion rod, and profiled head are arranged coaxially and in series, allowing for a smaller outer diameter and enabling a compact, elongated design that can be easily integrated into narrow spaces, with separate radial bearings for enhanced stability and a solid shaft design for the belt reel for increased rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the belt retractor is designed with a large cavity and large outer diameter belt reel to accommodate a two-stage torsion rod and torque tube, then the force-limiting function is achieved, but the installation space requirement increases and conflicts with limited backrest space
Solution Approach 1:
The torsion rod is extracted from the belt reel cavity and mounted externally on the belt reel perimeter. This allows the belt reel to be designed with a smaller outer diameter and without a large central cavity, thereby reducing the overall installation space footprint while maintaining the force-limiting function through the externally mounted torsion rod
Solution Approach 2:
The torsion rod is repositioned from a radial arrangement (within the belt reel cavity) to a tangential arrangement (on the external perimeter of the belt reel). This dimensional change in mounting location allows the force-limiting mechanism to function outside the traditional radial space constraints, enabling a more compact overall design
2Area of stationary object
If the belt retractor is designed to be compact and elongated for narrow backrest installation spaces, then the installation space requirement is reduced, but the structural rigidity and stability may be compromised
Solution Approach 1:
The belt reel is pre-mounted in the backrest with its rotation axis perpendicular to the backrest surface, establishing a stable baseline configuration. The torsion rod is then mounted on the perimeter of this pre-positioned belt reel, allowing the force-limiting function to be added without requiring extensive structural modifications to the backrest framework
Solution Approach 2:
The torsion rod is positioned at a specific location on the belt reel perimeter where it can effectively resist tensile forces during restraint events. This localized placement optimizes the force-limiting function while maintaining overall structural stability, as the torsion rod's positioning is specifically tailored to the local mechanical requirements rather than requiring global structural reinforcement
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 configuration allows for a more stable and compact belt retractor that can be easily installed in existing narrow spaces, with a stepped force-limiting characteristic achieved through the use of multiple torsion rods, effectively absorbing restraining forces during accidents.
Implementation Method 1
plastically deformable torsion rods have proven themselves effective and at one end are rotationally fixed to the belt reel
Implementation Method 2
a two-stage torsion rod with two torsion sections having different plastic deformation limits
Data Source
AI summary
The invention relates to a belt retractor surrounding a belt reel which is rotatably mounted in a frame, and comprising a force-limiting device with at least one plastically deformable first torsion rod, wherein the first torsion rod has a first end rotationally fixed to the belt reel and a second end rotationally fixed to a profiled head which can be blocked via a first blocking device in a fixed manner relative to the vehicle. The belt reel, the first torsion rod and the profiled head are arranged coaxially to one another and in series relative to one another.