Seat Belt Retractor Force Limiting With Motor-Triggered Blocking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing belt retractors in vehicles lack a controlled force limiting mechanism that can independently manage belt extension to reduce occupant load during accidents, relying on unchangeable force limiting characteristics defined by their design.
Innovation Solution
A belt retractor with a force limiting unit featuring an electric motor and a blocking device that releases and blocks the belt shaft's rotational movement in a repeating sequence, allowing for controlled, force-limited belt pull-out movements triggered by the electric motor, enabling independent control of the start and end of the belt pull-out movement regardless of tensile forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a force-limiting unit with a torsion bar is used, then a constant force-limiting level is provided, but the force-limiting characteristic is unchangeable and cannot be independently controlled
Solution Approach 1:
The patent replaces the purely mechanical torsion bar force-limiting system with an electromechanical system. An electric motor is integrated into the force-limiting unit to actively control the belt shaft's rotational movement. This substitution allows the force-limiting characteristic to be dynamically adjusted through electrical control signals, enabling independent management of belt extension regardless of the mechanical torsion bar's fixed properties.
Solution Approach 2:
The patent introduces dynamic control to the previously static force-limiting mechanism. The blocking device is designed to release and block the belt shaft's rotational movement in a repeating sequence, creating a dynamic, controllable force-limiting behavior. This allows the system to adapt the force-limiting characteristic in real-time based on control signals, transforming the unchangeable mechanical property into a dynamically adjustable parameter.
2Adaptability or versatility
If additional gear stages are provided to drive the belt shaft at different speeds and torques, then speed and torque control is improved, but the installation space required increases
Solution Approach 1:
The patent merges the force-limiting function with the drive mechanism into a single integrated force-limiting unit. The electric motor is positioned within the existing belt retractor structure, and the blocking device is arranged to interact directly with the belt shaft's rotation. This consolidation eliminates the need for separate gear stages and reduces the overall installation space while maintaining speed and torque control capabilities.
Solution Approach 2:
The electric motor in the force-limiting unit serves multiple functions: it provides the driving torque for belt shaft rotation, enables speed control through its inherent motor characteristics, and works with the blocking device to create the force-limiting effect. This multi-functionality replaces what would otherwise require separate mechanical components for each function, thereby reducing installation space requirements.
3Force
If the plastic deformation resistance of the torsion bar is not exceeded, then the belt tension is insufficient for proper force-limiting, but the occupant load becomes higher than necessary
Solution Approach 1:
The patent implements a feedback-controlled force-limiting mechanism. The blocking device monitors the rotational movement of the belt shaft and actively adjusts its blocking action based on control signals. This feedback control allows the system to maintain optimal belt tension by dynamically adjusting the force-limiting characteristic, ensuring that the minimum necessary force is applied to achieve proper force-limiting while minimizing excessive occupant load.
Solution Approach 2:
The patent enables dynamic change of the force-limiting parameter through electrical control. By adjusting the control signals to the electric motor and blocking device, the force-limiting characteristic can be modified in real-time. This allows optimization of the belt tension parameter to achieve the lowest effective force-limiting level that still provides adequate protection, thereby reducing harmful occupant load while maintaining sufficient belt tension.
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 allows for a controlled and reduced occupant load during accidents by enabling step-wise belt extension under occupant tensile forces, with the electric motor triggering the force-limited movement and the blocking device managing the belt pull-out process to minimize perceived discomfort.
Implementation Method 1
belt retractors in modern safety belt systems are equipped with electric motors which, when activated, drive the belt shaft in the winding direction
Implementation Method 2
The blocking device is spring-loaded relative to the belt shaft via a spring
Implementation Method 3
Steel torsion bars have proven particularly effective as force-limiting units. During activation, these torsion bars are plastically twisted around their longitudinal axis, thereby deliberately dissipating energy
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a belt retractor having a belt shaft (5), which is mounted rotatably in a frame (1) and on which a safety belt can be wound, and a force-limiting unit (61), which, when activated, allows a rotary movement of the belt shaft (5) in the extension direction of the safety belt, wherein the force-limiting unit (61) has an electric motor (4) and a first blocking device, and the first blocking device is designed, when actuated by the activation of the electric motor (4), to release a rotary movement of the belt shaft (5) in the extension direction and block it again in a recurring sequence.