Seat Belt Buckle Force-Limiting Assembly for Chest Load Relief

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Solution Overview

Problem

Existing seat belts do not adequately adjust to reduce force on the occupant's chest after a collision, compromising comfort while ensuring safety.

Innovation Solution

A buckle assembly with a force-limiting module that includes a mandrel, torsion bar, and winding component, allowing the seat belt to loosen when a predetermined force threshold is exceeded, reducing chest restraint by increasing the distance between the buckle and the force-limiting module.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the seat belt locking mechanism is activated to secure the occupant during collision, then the safety of the occupant is ensured, but the force applied to the chest of the occupant becomes excessive and uncomfortable

Engineering Contradiction:
Improvesafety of the occupantVSAvoidforce applied to the chest of the occupant
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The force-limiting module changes the mechanical parameter of the seat belt system by introducing a force threshold mechanism. When the force exceeds the predetermined threshold, the mandrel rotates and the winding component unwinds, allowing the seat belt to loosen and reduce the force applied to the occupant's chest while maintaining safety through the force-limiting function.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The seat belt system transitions from a static locked state to a dynamic adjustable state through the force-limiting module. The mandrel can rotate and the winding component can unwind when force exceeds the threshold, enabling the system to dynamically adjust the restraint force based on real-time conditions after collision.

Inventive Principle:
Principle #15Dynamics

2Reliability

If the seat belt is tightly secured to ensure safety during collision, then the occupant is properly restrained, but the comfort of the occupant is reduced due to excessive force on the chest

Engineering Contradiction:
Improveoccupant restraintVSAvoidcomfort of the occupant
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The force-limiting module introduces a force threshold parameter that automatically adjusts the seat belt tension. When the force exceeds this threshold, the system changes the restraint parameter by allowing the mandrel to rotate and the winding component to unwind, thereby reducing the force to a comfortable level while maintaining adequate restraint.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The force-limiting module operates autonomously based on the force threshold. When excessive force is detected, the system automatically activates the loosening mechanism through mandrel rotation and winding component unwinding, without requiring external intervention, thus balancing safety and comfort automatically.

Inventive Principle:
Principle #25Self-service

3Reliability

If the seat belt cannot be pulled out during collision, then the occupant is securely restrained, but the ability to adjust the seat belt after collision is lost

Engineering Contradiction:
Improveseat belt lockingVSAvoidseat belt adjustment after collision
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The seat belt system transitions from a static locked state to a dynamic adjustable state through the force-limiting module. After collision, when force exceeds the threshold, the mandrel rotates and the winding component unwinds, enabling the seat belt to loosen and adapt to the occupant's condition, thus providing both secure restraint and post-collision adjustability.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The force-limiting module provides mechanical feedback based on the force threshold. When the force exceeds the predetermined value, the system responds by allowing mandrel rotation and winding component unwinding, creating a feedback mechanism that automatically adjusts the seat belt tension based on the force conditions after collision.

Inventive Principle:
Principle #23Feedback

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

Improves occupant comfort by reducing excessive seat belt tension after a collision without compromising safety, ensuring appropriate restraint adjustment.

Implementation Method 1

the torsion bar undergoes torsional deformation by co-rotating with the mandrel at the only connected portion of the torsion bar

Methodology Applied
Scientific EffectTorsional deformation: Elasticity

Implementation Method 2

a winding component having a winding portion wound around an outer circumferential surface of the mandrel and a fixing portion fixed to the buckle; when a force applied to the buckle is greater than the force threshold defined by the force-limiting module, the torsion bar undergoes torsional deformation by co-rotating with the mandrel at the only connected portion of the torsion bar, while the winding portion of the winding component gradually unwinds from the outer circumferential surface of the mandrel as the mandrel rotates

Methodology Applied
Scientific EffectMechanical energy storage: Spring

Data Source

PatentEP4609744A1Buckle assembly and seat belt buckle
Publication Date: 2025.09.03 AUTOLIV DEV AB
  • EP4609744A1 patent drawingFigure 1(a)~2
  • EP4609744A1 patent drawingFigure 3~5
  • EP4609744A1 patent drawingFigure 6(a)~8(b)

AI summary

The present invention provides a buckle assembly and a seat belt buckle. The buckle assembly includes a buckle configured to engage with a latch plate to secure a seat belt to a seat. The buckle assembly further includes a force-limiting module connected to the buckle and configured to define a force threshold. The force-limiting module includes: a mandrel having a hollow structure and rotatably supported at two axial ends; a torsion bar positioned in a hollow inner cavity of the mandrel to be arranged coaxially with the mandrel, only a portion of the torsion bar being connected to the mandrel in a co-rotatable manner; and a winding component having a winding portion wound around an outer circumferential surface of the mandrel and a fixing portion fixed to the buckle. When a force applied to the buckle is greater than the force threshold defined by the force-limiting module, the torsion bar undergoes torsional deformation by co-rotating with the mandrel at the only connected portion of the torsion bar, while the winding portion of the winding component gradually unwinds from the outer circumferential surface of the mandrel as the mandrel rotates, so that the buckle can move to increase the distance between the buckle and the force-limiting module.