Blowout Resistant Fuel Injector Welds Using Relief Regions

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Solution Overview

Problem

Laser welding of tubular components in fuel injectors often results in 'blow-out' of the weld bead due to rapid internal pressure increases, leading to leaks and contamination, with existing techniques either causing voids or allowing slag to escape.

Innovation Solution

A method involving a non-contact region with a gap and a press-fit region, where the annular surfaces are shaped to create a sealed clearance area, allowing the weld bead to form without pressure differential issues, using laser welding with specific power and rotation settings to ensure a hermetic seal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If laser welding is performed on tubular components with press-fit regions, then hermetic seal is achieved, but weld blow-out occurs due to rapid pressure increase

Engineering Contradiction:

Improvehermetic sealVSAvoidweld blow-out

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The annular surface is divided into two distinct regions: a press-fit region for mechanical assembly and a non-contact region for welding. This segmentation allows the welding operation to occur in a zone free from press-fit constraints, eliminating the pressure differential that causes weld blow-out while maintaining the hermetic seal requirement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the annular surface are given different properties: the press-fit region has contact between surfaces for mechanical retention, while the non-contact region has a controlled gap to prevent pressure buildup during welding. This local differentiation resolves the contradiction between achieving hermetic seal and preventing weld blow-out.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If clearance is provided between facing surfaces to prevent blow-out, then weld blow-out is eliminated, but weld slag and oxides escape into the valve body

Engineering Contradiction:

Improveweld blow-out preventionVSAvoidinternal contamination

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The annular surface is segmented into a press-fit region that provides containment and a non-contact region that prevents blow-out. The press-fit region acts as a barrier that contains weld slag and oxides, preventing them from escaping into the valve body, while the non-contact region eliminates the pressure differential that causes blow-out.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The press-fit region serves as an intermediary structure that provides mechanical retention and containment. It acts as a barrier between the welding zone and the valve body interior, allowing the welding operation to proceed without blow-out while preventing contamination of the valve body.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If press-fit is used between components, then assembly is secured, but weld blow-out occurs during welding

Engineering Contradiction:

Improveassembly securityVSAvoidweld blow-out

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The annular surface is segmented into a press-fit region for secure assembly and a non-contact region for welding. This allows the component to benefit from both press-fit assembly security and blow-out-free welding by performing these operations in spatially separated zones.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different local regions of the annular surface have different characteristics: the press-fit region provides mechanical retention with surface contact, while the non-contact region provides a gap that prevents pressure buildup during welding. This local quality differentiation allows both assembly security and weld integrity to be achieved.

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

The solution effectively prevents 'blow-out' and contamination by forming a hermetic seal, maintaining the integrity of the weld and preventing internal contamination, while maintaining the press-fit requirement for assembly.

Implementation Method 1

welding the annular surfaces together in the non-contact region to form an annular weld bead

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

The resulting overlap of the weld ensures that the weld is hermetic

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 3

small cavities contain trapped air due to an imperfect surface finish of the components pressed together

Methodology Applied

Scientific EffectPressure containment: Pressure Gradient

Data Source

PatentUS7617605B2Component geometry and method for blowout resistant welds

Publication Date: 2009.11.17 VITESCO TECHNOLOGIES USA LLC

AI summary

In a method for reducing “blow-out” of annular welds for attaching components in a fuel injector, a relief region is formed on radially-facing surfaces of the components. The relief region is adjacent to a press-fit region. The components are then pressed together, and a weld is made in the relief region. A sealed gap is thereby formed in the relief region between the weld and the press-fit region. The sealed gap provides for the expansion of trapped gases that could otherwise “blow out” the liquid weld bead.