Three-Point Seatbelt with Coordinated Force Limiters

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Solution Overview

Problem

Existing three-point seatbelt devices face challenges in effectively managing load distribution during crashes, particularly in oblique crashes, due to the lack of coordinated activation of pre-tensioner and force limiter mechanisms, leading to potential failure of the force limiter mechanism in the retractor and increased load on the occupant.

Innovation Solution

A compact three-point seatbelt device design that includes a shoulder-side reeler with a pre-tensioner and force limiter mechanism, and an inner belt with a buckle-side force limiter mechanism, where the initial load of the buckle-side force limiter is set to be larger than the shoulder-side force limiter, allowing for effective activation of both mechanisms to reduce occupant load, without the need for electrical control units.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If both the retractor and inner belt include pre-tensioner mechanisms, then the occupant's chest load is reduced during crashes, but the device size increases and activation timing control becomes complex

Engineering Contradiction:

Improvechest load during crashVSAvoidseatbelt device size

Core Design Contradiction:

Object-affected harmful factorsVSVolume of moving object

Solution Approach 1:

The patent removes the pre-tensioner mechanism from the inner belt, extracting only the necessary force limiter mechanism. This eliminates the volume increase and control complexity associated with having two pre-tensioners, while maintaining chest load reduction through the coordinated operation of the retractor's pre-tensioner and the buckle-side force limiter.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent divides the protective function into two segments: the retractor handles pre-tensioning and shoulder-side force limiting, while the inner belt provides buckle-side force limiting. This segmentation allows each component to be optimized for its specific function, reducing overall device complexity while maintaining comprehensive protection.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If both pre-tensioner mechanisms are activated simultaneously, then chest load is reduced, but excessive load may be exerted on the occupant's chest

Engineering Contradiction:

Improvechest load during crashVSAvoidactivation timing control

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent changes the parameter of initial load between the two force limiter mechanisms. The buckle-side force limiter is designed with a higher initial load than the shoulder-side force limiter, ensuring sequential activation rather than simultaneous activation. This parameter differentiation automatically controls the timing and sequence of activation without requiring complex electrical control systems.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the FL mechanism of the retractor has the same activation load as the FL mechanism of the inner belt, then both mechanisms can be activated, but the retractor's FL mechanism may fail to activate effectively in oblique crashes

Engineering Contradiction:

ImproveFL mechanism activationVSAvoidoccupant load in oblique crash

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different local qualities to the two force limiter mechanisms by setting different initial loads. The shoulder-side force limiter has a lower initial load to activate first in oblique crashes, while the buckle-side force limiter has a higher initial load. This local differentiation ensures that the shoulder-side mechanism activates to protect against oblique crash loads before the buckle-side mechanism engages.

Inventive Principle:

Principle #3Local quality

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 design effectively reduces the load on the occupant's chest during crashes by ensuring coordinated activation of both force limiter mechanisms, even in oblique crashes, while maintaining a compact size and reducing manufacturing costs by eliminating the need for electrical control systems.

Implementation Method 1

the PT mechanism is activated during a crash, the webbing is pulled in from the shoulder side, so that any slack in the webbing can be removed

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Implementation Method 2

as the shoulder-side FL mechanism is activated, an excessive load exerted on the chest of the occupant restrained by the shoulder belt can be reduced

Methodology Applied

Scientific EffectDeformation: Deformation

Data Source

PatentUS10703332B2Three-point seatbelt device

Publication Date: 2020.07.07 TOYOTA JIDOSHA KK

AI summary

A three-point seatbelt device includes: a webbing configured to function as a shoulder belt and a lap belt; a shoulder-side reeler that includes a pre-tensioner mechanism and a shoulder-side force limiter mechanism, and is configured to reel up an end portion of the webbing on a shoulder belt side so as to allow the webbing to be pulled out; a tongue mounted on the webbing; and an inner belt including a buckle to which the tongue is coupled, the inner belt including, of a pre-tensioner mechanism and a buckle-side force limiter mechanism, only the buckle-side force limiter mechanism. An initial load of the buckle-side force limiter mechanism is set to be larger than an initial load of the shoulder-side force limiter mechanism.