Solenoid Injector Weld Zone Corrosion Prevention
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Solution Overview
Problem
The Continental Deka VII solenoid fluid injector's weld zone is susceptible to corrosive attacks from aqueous urea solutions and high ethanol fuels, leading to potential damage and failure, especially in environments where the fluid is stagnant and oxygenated, weakening the corrosion resistance of the stainless steel materials.
Innovation Solution
Incorporating a corrosion prevention structure, such as an elastomer plug made of EPDM or FKM rubber, is placed between the through-hole and the valve member to prevent the fluid from accessing the weld zone, using a spherical or cylindrical shape to minimize crevice volume and enhance resistance to corrosive fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser welding is used to join the ball and tube components, then manufacturing cost is reduced and assembly speed is improved, but the weld zone becomes susceptible to corrosive attacks from stagnant oxygenated fluid
Solution Approach 1:
A corrosion-resistant liner material is introduced as an intermediary layer between the weld zone and the corrosive fluid. This liner acts as a mediator that protects the vulnerable weld area from direct contact with stagnant oxygenated fluid, thereby maintaining both the cost-effectiveness of laser welding and the corrosion resistance required for reliability in harsh environments
Solution Approach 2:
A thin film or coating of corrosion-resistant material is applied to the weld zone and crevice areas. This protective film creates a barrier that prevents corrosive fluid from attacking the weld metal, allowing the use of inexpensive laser-welded assemblies while maintaining durability in corrosive conditions
2Ease of manufacture
If the injector uses stainless steel materials with weld zones, then manufacturing cost is reduced compared to alternative joining methods, but the weld heat affected zone experiences weakened corrosion resistance
Solution Approach 1:
Instead of requiring the entire injector to be made from expensive corrosion-resistant materials or complex multi-piece constructions, the solution applies localized protection only to the vulnerable weld zones and crevice areas. This targeted approach maintains cost-effectiveness while providing adequate corrosion resistance where it is most needed
Solution Approach 2:
The injector employs a composite structure combining standard stainless steel components with localized corrosion-resistant coatings or liners in the weld zones. This composite approach allows the bulk material to remain cost-effective while the protective layer provides enhanced corrosion resistance at critical interfaces
3Reliability
If the crevice volume at the weld joint is reduced, then corrosion resistance is improved, but the manufacturing complexity increases
Solution Approach 1:
The solution uses inexpensive, easily applied protective coatings or sacrificial liner materials that can be straightforwardly manufactured into the weld zones. These simple, cost-effective protective layers reduce crevice corrosion risk without requiring complex structural modifications to the injector design
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 elastomer plug effectively prevents corrosion at the weld zone by isolating the fluid from the critical areas, ensuring the longevity and reliability of the injector even in corrosive environments, while maintaining cost-effectiveness.
Implementation Method 1
Corrosion prevention structure is disposed in the tube between the through-hole and the valve member, and is constructed and arranged to prevent the fluid in the tube from accessing the weld zone
Data Source
AI summary
A fluid injector includes a valve structure movable in the passageway between a first position and a second position. The valve structure includes a hollow tube having a longitudinal axis and a valve member connected to an end of the tube by a weld, with a weld zone being defined inside of the tube generally adjacent to the weld. The tube has surfaces defining a through-hole that is disposed transversely with respect to the longitudinal axis of the tube. The through-hole permits the fluid to enter an interior of the tube. Corrosion prevention structure is disposed in the tube between the through-hole and the valve member to prevent the fluid in the tube from accessing the weld zone.