Belt Retractor Axial Decoupling Mechanism
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Solution Overview
Problem
Existing belt retractors face interference issues between the pinion and load transmission element during the unwinding phase of the load limiting phase, which can impede the controlled rotation of the belt reel, potentially increasing the load on vehicle occupants.
Innovation Solution
A decoupling mechanism that axially moves the pinion away from the belt reel, using a ramp or gear construction to ensure independent rotation of the belt reel during the load limiting phase, preventing torque transfer from the pinion and load transmission element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pinion remains coupled to the belt reel during the load limiting phase, then the belt tensioning function is maintained, but the controlled unwinding rotation of the belt reel is impeded or blocked
Solution Approach 1:
The pinion-belt reel coupling is made dynamic through a decoupling mechanism that transitions the system from a coupled state during belt tensioning to an uncoupled state during load limiting. The pinion can axially disengage from the belt reel teeth, allowing the belt reel to rotate independently in the unwinding direction while the pinion remains engaged with the load transmission element for continued load limitation.
2Reliability
If the load transmission element continues to engage the pinion during the load limiting phase, then load limitation is maintained, but the belt reel rotation in unwinding direction is blocked
Solution Approach 1:
The coupling between the load transmission element and the belt reel is segmented into two independent pathways: (1) the pinion-load transmission element pathway that remains engaged for load limitation, and (2) the belt reel unwinding pathway that is freed through axial decoupling. This allows the load transmission element to continue limiting load through the pinion while the belt reel rotates freely in the unwinding direction.
3Force
If a traditional rack-and-pinion tensioner is used, then the belt tensioning force is sufficient, but the tooth-on-tooth contact causes rough operation and interference during unwinding
Solution Approach 1:
The patent introduces a deformable load transmission element as an intermediary between the pinion and the belt reel. This element replaces direct tooth-on-tooth contact with a smoother engagement mechanism that allows the pinion to rotate the belt reel during tensioning without the roughness of direct gear contact, and enables clean decoupling during load limiting.
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
Enables controlled and interference-free rotation of the belt reel in the unwinding direction, effectively limiting the load on vehicle occupants and preventing excessive force application during the load limiting phase.
Implementation Method 1
a ramp or gear construction to ensure independent rotation of the belt reel
Implementation Method 2
the load transmission element forces the pinion - and the belt reel coupled thereto - to rotate as long as the teeth of the pinion engage the load transmission element in a force transmitting manner
Data Source
Figure 1~2
Figure 3a~5b
Figure 6a~8b
AI summary
A belt retractor (10) for a vehicle safety belt system comprises a belt tensioner for tensioning a safety belt during a belt tensioning phase, and a load limiter for limiting the load applied by the safety belt on a vehicle occupant during a load limiting phase after the belt tensioning phase. The belt tensioner includes a frame (12), a belt reel (14), a toothed pinion (22), a drive unit (16) and an elongated load transmission element (20). The belt reel (14) is rotatably supported in the frame (12), and the pinion (22) is coupled to the belt reel (14). During the belt tensioning phase the load transmission element (20) engages the teeth of the pinion (22). The belt tensioner further includes a decoupling mechanism for decoupling the belt reel (14) from the pinion (22) at the end of the belt tensioning phase.