Vehicle Inflator With Weakened Zone Component

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Solution Overview

Problem

Existing inflators for vehicle occupant restraint systems face challenges in quickly releasing gas for airbag inflation due to limitations in the design of the propellant generation and membrane opening mechanism, leading to inefficient gas discharge.

Innovation Solution

Incorporating a component with a weakened zone between the combustion chamber and storage chamber, which creates a larger discharge orifice upon activation, generating a shock wave to quickly open the membrane and facilitate gas flow, along with overflow orifices for pressure compensation, reducing the need for welding and enhancing the igniter's gas-tightness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a membrane enclosing the storage chamber is used to contain pressurized gas, then gas containment is improved, but the membrane opening speed is insufficient

Engineering Contradiction:

Improvegas containmentVSAvoidmembrane opening speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent creates a shock wave path in advance through the component design, which is triggered by the igniter to rapidly open the membrane. The component acts as a pre-positioned shock wave generator that, when activated, immediately propagates through the pressurized gas to burst the membrane at optimal location and timing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes shock wave generation as a form of mechanical disturbance to rapidly open the membrane. The shock wave creates a pressure front that propagates through the gas and forcefully opens the membrane, achieving much faster opening speeds compared to gradual pressure buildup.

Inventive Principle:

Principle #18Mechanical vibration

2Speed

If a component with weakened zone is introduced to create larger discharge orifice, then gas discharge speed is improved, but device complexity increases

Engineering Contradiction:

Improvegas discharge speedVSAvoidcomponent structure

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The component is divided into a weakened zone and intact zones. The weakened zone is specifically designed with reduced material strength or pre-formed discontinuities, allowing it to fail first and create a large opening when exposed to shock waves, while the rest of the component maintains structural integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The component with the weakened zone acts as an intermediary element between the combustion chamber and storage chamber. It controls the gas flow path and timing, using the shock wave to trigger the weakened zone's failure, thereby mediating the rapid gas discharge process.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If welding is used to connect the membrane to the housing component, then connection strength is improved, but manufacturing complexity and time increase

Engineering Contradiction:

Improvemembrane connection strengthVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent replaces the welding process (thermal/mechanical joining) with a press-fit mechanical interference fit system. The component is pressed into the housing with sufficient force to create a tight, pressure-resistant connection without requiring thermal processes, simplifying manufacturing while maintaining connection strength.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If overflow orifices are added for pressure compensation, then pressure balance is improved, but pressure loss increases

Engineering Contradiction:

Improvepressure compensationVSAvoidpressure loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The overflow orifices are strategically positioned and sized to provide localized pressure compensation only where needed. The small cross-sectional area of the orifices is optimized to allow just enough flow for pressure balancing during normal operation, minimizing pressure loss while maintaining reliability.

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 enables faster and more efficient gas discharge from the inflator, ensuring quick and safe opening of the membrane, even under high pressures, with minimal pressure loss through overflow orifices, thus improving the inflator's performance and reducing manufacturing complexity.

Implementation Method 1

a shock wave can be generated by which the outlet membrane of the storage chamber can be opened more quickly

Methodology Applied

Scientific EffectShock wave: Shock Wave

Implementation Method 2

a combustion chamber in which solid propellant adapted to be burnt off while forming gas is accommodated

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS8651520B2Inflator

Publication Date: 2014.02.18 TRW AIRBAG SYSTEMS GMBH

AI summary

An inflator (10), especially for a vehicle occupant restraint system, comprising a combustion chamber (24) in which solid propellant (28) adapted to be burnt off while forming a gas is accommodated, a storage chamber (26) containing a pressure gas (30), an igniter (14) and a component (20) arranged between the combustion chamber (24) and the storage chamber (26). There is at least one flow communication between the storage chamber (26) and the combustion chamber (24). The component (20) includes an additional weakened zone (22) adapted to be destroyed upon activation of the inflator (10) so as to permit flow of gas from the combustion chamber (24) into the storage chamber (26).