Pretensioner Tube Exit Guide for Tangential Drive Gear Engagement

Solution Overview

Problem

In existing belt tensioners, the load transmission element often fails to regain a straight shape after being curved during long dwell times within the tensioner tube, leading to improper tangential engagement with the drive gear, which can result in misalignment and reduced effectiveness.

Innovation Solution

A wound tensioner tube with an elongate inwardly protruding projection adjacent to the exit end, where the projection's longitudinal axis is inclined against the tube's longitudinal axis, interacts with the load transmission element to counteract curvature and ensure a largely tangential introduction into the drive gear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the load transmission element is guided through a curved tensioner tube for long dwell times, then space-saving compact design is achieved, but the load transmission element fails to regain straight shape and impacts the drive gear improperly

Engineering Contradiction:

Improvespace-saving compact designVSAvoidalignment precision with drive gear

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The tensioner tube is pre-formed with an elongate projection that protrudes into the tube interior at a specific inclination angle (5°-20°) relative to the tube axis. This preliminary structural feature is designed to actively guide the load transmission element during its movement, ensuring it exits in the correct tangential direction relative to the drive gear, thereby preventing misalignment after long dwell times.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The elongate projection inside the tensioner tube acts as an intermediary guiding element. It mediates between the curved tube path and the straight exit requirement by providing a physical surface that the load transmission element contacts, forcing it to follow the intended trajectory and exit tangentially to the drive gear.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If the load transmission element is made deformable for damped actuation, then high torque transmission is ensured, but curvature accumulates during dwell time causing engagement issues

Engineering Contradiction:

Improvetorque transmissionVSAvoidshape stability

Core Design Contradiction:

PowerVSStability of the object's composition

Solution Approach 1:

The elongate projection in the tensioner tube applies a counteracting force to the curvature that accumulates in the deformable load transmission element during dwell time. By contacting the element at a specific angle, the projection actively prevents the element from adopting an incorrect curved shape, ensuring it maintains the proper straight configuration for tangential engagement with the drive gear.

Inventive Principle:

Principle #9Preliminary anti-action

3Manufacturing precision

If the tensioner tube exit is made tangent to the drive gear, then proper engagement is intended, but long dwell times cause the load transmission element to curve and miss the tangent path

Engineering Contradiction:

Improveengagement alignmentVSAvoiddwell time

Core Design Contradiction:

Manufacturing precisionVSDuration of action of moving object

Solution Approach 1:

The tensioner tube is pre-formed with an elongate projection that protrudes into the tube interior at a specific inclination angle (5°-20°) relative to the tube axis. This preliminary structural feature is designed to actively guide the load transmission element during its movement, ensuring it exits in the correct tangential direction relative to the drive gear, thereby preventing misalignment after long dwell times.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The elongate projection inside the tensioner tube acts as an intermediary guiding element. It mediates between the curved tube path and the straight exit requirement by providing a physical surface that the load transmission element contacts, forcing it to follow the intended trajectory and exit tangentially to the drive gear.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12240413B2Pretensioner tube for a belt tensioner

Publication Date: 2025.03.04 ZF AUTOMOTIVE GERMANY GMBH

AI summary

A tensioner tube (18) for guiding a load transmission element (20) for a belt tensioner comprises an exit end (32) and a tube section (34) adjacent to the exit end (32), the tube section (34) being configured and arranged so that the longitudinal axis (L) of the tube section (34) is substantially tangent to the drive gear (14), wherein an elongate projection (36) protruding into the interior of the tube, the longitudinal axis (I) of which is inclined in relation to the longitudinal axis (L) of the tube section (34), is formed in the tube section (34) adjacent to the exit end (32). A belt tensioner for a seat belt system comprises a pyrotechnically movable load transmission element (20) and a drive gear (14) which can be driven by the movable load transmission element (20). The load transmission element (20) is guided in a tensioner tube (18) of the above-mentioned type.